selftests/nolibc: run-tests.sh: avoid overwriting CFLAGS_EXTRA

If the user specified their own CFLAGS_EXTRA these should not be
overwritten by `-e`.

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20240807-nolibc-llvm-v2-12-c20f2f5fc7c2@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

tools/testing/selftests/nolibc/run-tests.sh

@@ -15,7 +15,7 @@ download_location="${cache_dir}/crosstools/"
 build_location="$(realpath "${cache_dir}"/nolibc-tests/)"
 perform_download=0
 test_mode=system
-CFLAGS_EXTRA="-Werror"
+werror=1
 archs="i386 x86_64 arm64 arm mips32le mips32be ppc ppc64 ppc64le riscv s390 loongarch"
 
 TEMP=$(getopt -o 'j:d:c:b:a:m:peh' -n "$0" -- "$@")
@@ -69,7 +69,7 @@ while true; do
 			test_mode="$2"
 			shift 2; continue ;;
 		'-e')
-			CFLAGS_EXTRA=""
+			werror=0
 			shift; continue ;;
 		'-h')
 			print_usage
@@ -140,6 +140,9 @@ test_arch() {
 	ct_abi=$(crosstool_abi "$1")
 	cross_compile=$(realpath "${download_location}gcc-${crosstool_version}-nolibc/${ct_arch}-${ct_abi}/bin/${ct_arch}-${ct_abi}-")
 	build_dir="${build_location}/${arch}"
+	if [ "$werror" -ne 0 ]; then
+		CFLAGS_EXTRA="$CFLAGS_EXTRA -Werror"
+	fi
 	MAKE=(make -j"${nproc}" XARCH="${arch}" CROSS_COMPILE="${cross_compile}" O="${build_dir}")
 
 	mkdir -p "$build_dir"