Incorrect compiler -fstack-clash-protection warnings on Apple/M1/Clang

[clanmills]

On macOS on the M1 (arm64) chip, CMake sets -fstack-clash-protection. The compiler produces numerous warnings such as:

[ 99%] Building CXX object samples/CMakeFiles/addmoddel.dir/addmoddel.cpp.o clang: warning: argument unused during compilation: '-fstack-clash-protection' [-Wunused-command-line-argument]

My fix is:

diff --git a/cmake/compilerFlags.cmake b/cmake/compilerFlags.cmake
index 35faf50..f0d64e2 100644
--- a/cmake/compilerFlags.cmake
+++ b/cmake/compilerFlags.cmake
@@ -23,13 +23,17 @@ if ( MINGW OR UNIX OR MSYS ) # MINGW, Linux, APPLE, CYGWIN
 
 
     if (COMPILER_IS_GCC OR COMPILER_IS_CLANG)
-        # This fails under Fedora - MinGW - Gcc 8.3
+        # This fails under Fedora - MinGW - Gcc 8.3 and macOS/M1^M
         if (NOT (MINGW OR CYGWIN OR CMAKE_HOST_SOLARIS))
-            check_cxx_compiler_flag(-fstack-clash-protection HAS_FSTACK_CLASH_PROTECTION)
+            # macOS M1 will set ARCHITECTURE == arm64^M
+            EXECUTE_PROCESS( COMMAND uname -m COMMAND tr -d '\n' OUTPUT_VARIABLE ARCHITECTURE )^M
+            if ( NOT ${ARCHITECTURE} STREQUAL arm64 )^M
+                check_cxx_compiler_flag(-fstack-clash-protection HAS_FSTACK_CLASH_PROTECTION)^M
+            endif()^M
             check_cxx_compiler_flag(-fcf-protection HAS_FCF_PROTECTION)
             check_cxx_compiler_flag(-fstack-protector-strong HAS_FSTACK_PROTECTOR_STRONG)
             if(HAS_FSTACK_CLASH_PROTECTION)
-                add_compile_options(-fstack-clash-protection)
+                add_compile_options(-fstack-clash-protection) ^M
             endif()
             if(HAS_FCF_PROTECTION)
                 add_compile_options(-fcf-protection)

[kevinbackhouse]

@clanmills: do you want this on both 0.27-maintenance and main?

[clanmills]

@kevinbackhouse yes, please.

There's mysterious ^M (carriage-return) chars in the patch.