Can't build GCC on Ubuntu

[sammtan]

1. I got the correct macOS SDK, version 15.1 @ Xcode 16.1
2. I'm on Ubuntu 22.04, already performed sudo apt-get install llvm-dev uuid-dev cpio libbz2-dev zlib1g-dev xzip lzma-dev libssl-dev bzip2 patch git libxml2-dev gcc g++ libmpc-dev libmpfr-dev libgmp-dev make clang. Though clang was modified later after successfully running build.sh
3. Running build_gcc.sh gives me this output (few last lines on the terminal):

/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/build/gcc-13.2.0/build/./gcc/xgcc -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/build/gcc-13.2.0/build/./gcc/ -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/bin/ -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/lib/ -isystem /home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/include -isystem /home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/sys-include    -O2  -g -O2 -DIN_GCC  -DCROSS_DIRECTORY_STRUCTURE  -W -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition  -isystem ./include  -mmacosx-version-min=10.8 -fno-common -g -DIN_LIBGCC2 -fbuilding-libgcc -fno-stack-protector   -dynamiclib -nodefaultlibs -install_name /home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/lib/libgcc_s.1.1.dylib -single_module -o ./libgcc_s.dylib -Wl,-exported_symbols_list,libgcc.map -compatibility_version 1 -current_version 1.1 -g -O2 -B./ _muldi3_s.o _negdi2_s.o _lshrdi3_s.o _ashldi3_s.o _ashrdi3_s.o _cmpdi2_s.o _ucmpdi2_s.o _clear_cache_s.o _trampoline_s.o __main_s.o _absvsi2_s.o _absvdi2_s.o _addvsi3_s.o _addvdi3_s.o _subvsi3_s.o _subvdi3_s.o _mulvsi3_s.o _mulvdi3_s.o _negvsi2_s.o _negvdi2_s.o _ctors_s.o _ffssi2_s.o _ffsdi2_s.o _clz_s.o _clzsi2_s.o _clzdi2_s.o _ctzsi2_s.o _ctzdi2_s.o _popcount_tab_s.o _popcountsi2_s.o _popcountdi2_s.o _paritysi2_s.o _paritydi2_s.o _powisf2_s.o _powidf2_s.o _powixf2_s.o _powitf2_s.o _mulsc3_s.o _muldc3_s.o _mulxc3_s.o _multc3_s.o _divsc3_s.o _divdc3_s.o _divxc3_s.o _divtc3_s.o _bswapsi2_s.o _bswapdi2_s.o _clrsbsi2_s.o _clrsbdi2_s.o _fixunssfsi_s.o _fixunsdfsi_s.o _fixunsxfsi_s.o _fixsfdi_s.o _fixdfdi_s.o _fixxfdi_s.o _fixunssfdi_s.o _fixunsdfdi_s.o _fixunsxfdi_s.o _floatdisf_s.o _floatdidf_s.o _floatdixf_s.o _floatundisf_s.o _floatundidf_s.o _floatundixf_s.o _fixsfti_s.o _fixdfti_s.o _fixxfti_s.o _fixtfti_s.o _fixunssfti_s.o _fixunsdfti_s.o _fixunsxfti_s.o _fixunstfti_s.o _floattisf_s.o _floattidf_s.o _floattixf_s.o _floattitf_s.o _floatuntisf_s.o _floatuntidf_s.o _floatuntixf_s.o _floatuntitf_s.o _divdi3_s.o _moddi3_s.o _divmoddi4_s.o _udivdi3_s.o _umoddi3_s.o _udivmoddi4_s.o _udiv_w_sdiv_s.o darwin-64_s.o cpuinfo_s.o sfp-exceptions_s.o _divhc3_s.o _mulhc3_s.o addtf3_s.o divtf3_s.o eqtf2_s.o getf2_s.o letf2_s.o multf3_s.o negtf2_s.o subtf3_s.o unordtf2_s.o fixtfsi_s.o fixunstfsi_s.o floatsitf_s.o floatunsitf_s.o fixtfdi_s.o fixunstfdi_s.o floatditf_s.o floatunditf_s.o fixtfti_s.o fixunstfti_s.o floattitf_s.o floatuntitf_s.o extendhfsf2_s.o extendhfdf2_s.o extendhftf2_s.o extendhfxf2_s.o extendsfdf2_s.o extendsftf2_s.o extenddftf2_s.o extendxftf2_s.o extendbfsf2_s.o trunctfhf2_s.o truncxfhf2_s.o truncdfhf2_s.o truncsfhf2_s.o trunctfsf2_s.o truncdfsf2_s.o trunctfdf2_s.o trunctfxf2_s.o trunctfbf2_s.o truncxfbf2_s.o truncdfbf2_s.o truncsfbf2_s.o trunchfbf2_s.o fixhfti_s.o fixunshfti_s.o floattihf_s.o floatuntihf_s.o floattibf_s.o floatuntibf_s.o eqhf2_s.o enable-execute-stack_s.o emutls_s.o libgcc.a -lSystem
MLIBS=`/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/build/gcc-13.2.0/build/./gcc/xgcc -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/build/gcc-13.2.0/build/./gcc/ -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/bin/ -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/lib/ -isystem /home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/include -isystem /home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/sys-include    --print-multi-lib | sed -e 's/;.*$//'` ; \
for mlib in $MLIBS ; do \
  cp ../${mlib}/libgcc/${mlib}/libgcc_s.dylib  \
    ./libgcc_s.1.1.dylib_T_${mlib} || exit 1 ; \
done
x86_64-apple-darwin24.1-lipo -output libgcc_s.1.1.dylib \
  -create libgcc_s.1.1.dylib_T*
rm libgcc_s.1.1.dylib_T*
MLIBS=`/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/build/gcc-13.2.0/build/./gcc/xgcc -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/build/gcc-13.2.0/build/./gcc/ -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/bin/ -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/lib/ -isystem /home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/include -isystem /home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/sys-include    --print-multi-lib | sed -e 's/;.*$//'` ; \
for mlib in $MLIBS ; do \
  cp ../${mlib}/libgcc/${mlib}/libgcc_s.dylib  \
    ./libgcc_s.1.1.dylib_T_${mlib} || exit 1 ; \
  arch=`x86_64-apple-darwin24.1-lipo -info libgcc_s.1.1.dylib_T_${mlib} | sed -e 's/.*:\ //'` ; \
  /home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/build/gcc-13.2.0/build/./gcc/xgcc -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/build/gcc-13.2.0/build/./gcc/ -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/bin/ -B/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/lib/ -isystem /home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/include -isystem /home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/sys-include    -arch ${arch} -nodefaultlibs -dynamiclib \
    -o libgcc_s.1.dylib_T_${mlib} \
    -Wl,-reexport_library,libgcc_s.1.1.dylib_T_${mlib} \
    -lSystem \
    -Wl,-reexported_symbols_list,../../../libgcc/config/darwin-unwind.ver \
    -install_name /home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/target/bin/../x86_64-apple-darwin24.1/lib/libgcc_s.1.dylib \
    -compatibility_version 1 -current_version 1 ; \
done
Undefined symbols for architecture x86_64:
  "___deregister_frame_info", referenced from:
     -reexported_symbols_list command line option
  "___deregister_frame_info_bases", referenced from:
     -reexported_symbols_list command line option
  "___register_frame_info", referenced from:
     -reexported_symbols_list command line option
  "___register_frame_info_bases", referenced from:
     -reexported_symbols_list command line option
  "___register_frame_info_table", referenced from:
     -reexported_symbols_list command line option
  "___register_frame_info_table_bases", referenced from:
     -reexported_symbols_list command line option
  "___register_frame_table", referenced from:
     -reexported_symbols_list command line option
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
make[2]: *** [../../../libgcc/config/t-slibgcc-darwin:139: libgcc_s.1.dylib] Error 1
make[2]: *** Waiting for unfinished jobs....
make[2]: Leaving directory '/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/build/gcc-13.2.0/build/x86_64-apple-darwin24.1/libgcc'
make[1]: *** [Makefile:13302: all-target-libgcc] Error 2
make[1]: Leaving directory '/home/sam/Documents/Pro-U/Externals/UsedRepos/osxcross/build/gcc-13.2.0/build'
make: *** [Makefile:1039: all] Error 2

exiting with abnormal exit code (2)
run 'OCDEBUG=1 ./build_gcc.sh' to enable debug messages

Why is that? Am I not supposed to have GCC for OSXCross on Ubuntu? Is it only for macOS, so it can compile for target Linux?
4. So far, successfully running compilers looks like below:

sam@sam:~/Documents/Pro-U/Externals/UsedRepos/osxcross$ o64-clang++ -v
clang version 17.0.6 (https://github.com/tpoechtrager/osxcross 29fe6dd35522073c9df5800f8cd1feb4b9a993a8)
Target: x86_64-apple-darwin24.1
Thread model: posix
InstalledDir: /usr/local/bin
Found CUDA installation: /usr/lib/cuda, version 11.5
sam@sam:~/Documents/Pro-U/Externals/UsedRepos/osxcross$ x86_64-apple-darwin24.1-clang++ -v
clang version 17.0.6 (https://github.com/tpoechtrager/osxcross 29fe6dd35522073c9df5800f8cd1feb4b9a993a8)
Target: x86_64-apple-darwin24.1
Thread model: posix
InstalledDir: /usr/local/bin
Found CUDA installation: /usr/lib/cuda, version 11.5
sam@sam:~/Documents/Pro-U/Externals/UsedRepos/osxcross$ oa64-clang++ -v
clang version 17.0.6 (https://github.com/tpoechtrager/osxcross 29fe6dd35522073c9df5800f8cd1feb4b9a993a8)
Target: arm64-apple-darwin24.1
Thread model: posix
InstalledDir: /usr/local/bin
Found CUDA installation: /usr/lib/cuda, version 11.5
sam@sam:~/Documents/Pro-U/Externals/UsedRepos/osxcross$ arm64-apple-darwin24.1-clang++ -v
clang version 17.0.6 (https://github.com/tpoechtrager/osxcross 29fe6dd35522073c9df5800f8cd1feb4b9a993a8)
Target: arm64-apple-darwin24.1
Thread model: posix
InstalledDir: /usr/local/bin
Found CUDA installation: /usr/lib/cuda, version 11.5
sam@sam:~/Documents/Pro-U/Externals/UsedRepos/osxcross$ oa64e-clang++ -v
clang version 17.0.6 (https://github.com/tpoechtrager/osxcross 29fe6dd35522073c9df5800f8cd1feb4b9a993a8)
Target: arm64e-apple-darwin24.1
Thread model: posix
InstalledDir: /usr/local/bin
Found CUDA installation: /usr/lib/cuda, version 11.5
sam@sam:~/Documents/Pro-U/Externals/UsedRepos/osxcross$ arm64e-apple-darwin24.1-clang++ -v
clang version 17.0.6 (https://github.com/tpoechtrager/osxcross 29fe6dd35522073c9df5800f8cd1feb4b9a993a8)
Target: arm64e-apple-darwin24.1
Thread model: posix
InstalledDir: /usr/local/bin
Found CUDA installation: /usr/lib/cuda, version 11.5