Use -Wno-unused-but-set-variable for Cryptlib and OpenSSL

Cryptlib and OpenSSL both currently throw warnings with some compilers
using -Wunused-but-set-variable:

  clang -std=gnu11 -ggdb -ffreestanding -fmacro-prefix-map=/home/pjones/devel/github.com/shim/main/= -fno-stack-protector -fno-strict-aliasing -fpic -fshort-wchar -nostdinc -m64 -mno-mmx -mno-sse -mno-red-zone  -Os -Wall -Wextra -Wno-missing-field-initializers -Wno-unused-parameter -Werror -I/home/pjones/devel/github.com/shim/main/Cryptlib -I/home/pjones/devel/github.com/shim/main/Cryptlib/Include -I/home/pjones/devel/github.com/shim/main/gnu-efi/inc -I/home/pjones/devel/github.com/shim/main/gnu-efi/inc/x86_64 -I/home/pjones/devel/github.com/shim/main/gnu-efi/inc/protocol -isystem /home/pjones/devel/github.com/shim/main/include/system -isystem /usr/lib64/clang/16/include -DMDE_CPU_X64   -c -o Pk/CryptX509.o Pk/CryptX509.c
Pk/CryptX509.c:94:19: error: variable 'Index' set but not used [-Werror,-Wunused-but-set-variable]
    UINTN           Index;
                    ^
  clang -std=gnu11 -ggdb -ffreestanding -fmacro-prefix-map=/home/pjones/devel/github.com/shim/main/= -fno-stack-protector -fno-strict-aliasing -fpic -fshort-wchar -nostdinc -m64 -mno-mmx -mno-sse -mno-red-zone  -Os -Wall -Wextra -Wno-missing-field-initializers -Wno-empty-body -Wno-implicit-fallthrough   -Wno-unused-parameter -Werror -I/home/pjones/devel/github.com/shim/main/Cryptlib/OpenSSL -I/home/pjones/devel/github.com/shim/main/Cryptlib -I/home/pjones/devel/github.com/shim/main/Cryptlib/OpenSSL/Include/ -I/home/pjones/devel/github.com/shim/main/Cryptlib/OpenSSL/crypto -I/home/pjones/devel/github.com/shim/main/Cryptlib/Include -I/home/pjones/devel/github.com/shim/main/gnu-efi/inc -I/home/pjones/devel/github.com/shim/main/gnu-efi/inc/x86_64 -I/home/pjones/devel/github.com/shim/main/gnu-efi/inc/protocol -I/home/pjones/devel/github.com/shim/main/Cryptlib/OpenSSL/crypto/asn1 -I/home/pjones/devel/github.com/shim/main/Cryptlib/OpenSSL/crypto/evp -I/home/pjones/devel/github.com/shim/main/Cryptlib/OpenSSL/crypto/modes -I/home/pjones/devel/github.com/shim/main/Cryptlib/OpenSSL/crypto/include -isystem /home/pjones/devel/github.com/shim/main/include/system -isystem /usr/lib64/clang/16/include -DL_ENDIAN -D_CRT_SECURE_NO_DEPRECATE -D_CRT_NONSTDC_NO_DEPRECATE -DOPENSSL_SMALL_FOOTPRINT -DPEDANTIC -DMDE_CPU_X64   -c -o crypto/asn1/t_x509.o crypto/asn1/t_x509.c
crypto/asn1/t_x509.c:504:18: error: variable 'l' set but not used [-Werror,-Wunused-but-set-variable]
      int ret = 0, l, i;
                   ^

Since we normally build with -Werror, these cause builds to fail in
these cases.  While the bad code should be addressed, it appears
generally safe, so we should solve it upstream.

This patch adds -Wno-unused-but-set-variable to the Cryptlib Makefile,
and removes the conditionalization on gcc in the OpenSSL Makefile, as
clang now has this argument, and since we don't support building with
clang for the final build, it's useful to have clang-based tools
working.

Signed-off-by: Peter Jones <[email protected]>

Cryptlib/Makefile

@@ -11,7 +11,8 @@ INCLUDES	= -I$(CRYPTDIR) -I$(CRYPTDIR)/Include \
 		  -isystem $(TOPDIR)/include/system \
 		  -isystem $(shell $(CC) -print-file-name=include)
 
-WARNFLAGS	+= -Wno-unused-parameter
+WARNFLAGS	+= -Wno-unused-parameter \
+		   -Wno-unused-but-set-variable
 
 CFLAGS		= $(FEATUREFLAGS) \
 		  $(OPTIMIZATIONS) \

Cryptlib/OpenSSL/Makefile

@@ -23,7 +23,7 @@ FEATUREFLAGS	+= -nostdinc
 WARNFLAGS	+= -Wno-empty-body \
 		   -Wno-implicit-fallthrough \
 		   $(if $(findstring gcc,$(CC)),-Wno-old-style-declaration) \
-		   $(if $(findstring gcc,$(CC)),-Wno-unused-but-set-variable) \
+		   -Wno-unused-but-set-variable \
 		   -Wno-unused-parameter
 
 CFLAGS		= $(FEATUREFLAGS) \