x86/build: Remove -ffreestanding on i386 with GCC

The use of -ffreestanding is a leftover that is only needed for certain
versions of Clang. Adjust this to be Clang-only. A later patch will make
this a versioned check.

Acked-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20250308042929.1753543-1-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

Author: kees

arch/x86/Makefile

@@ -137,8 +137,10 @@ ifeq ($(CONFIG_X86_32),y)
         include $(srctree)/arch/x86/Makefile_32.cpu
         KBUILD_CFLAGS += $(cflags-y)
 
-        # temporary until string.h is fixed
+    ifeq ($(CONFIG_CC_IS_CLANG),y)
+        # https://github.com/llvm/llvm-project/issues/53645
         KBUILD_CFLAGS += -ffreestanding
+    endif
 
     ifeq ($(CONFIG_STACKPROTECTOR),y)
         ifeq ($(CONFIG_SMP),y)