Kconfig: Have CONFIG_ASAN depend on COMPILER_GCC

-fsanitize=kernel-address is not implemented in clang

Change-Id: Ib8660bf99b940ff9eac7461f5946df0891dd3a4f
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63064
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/Kconfig

@@ -312,6 +312,7 @@ config ASAN
 	default n
 	select ASAN_IN_ROMSTAGE if HAVE_ASAN_IN_ROMSTAGE
 	select ASAN_IN_RAMSTAGE if HAVE_ASAN_IN_RAMSTAGE
+	depends on COMPILER_GCC
 	help
 	  Enable address sanitizer - runtime memory debugger,
 	  designed to find out-of-bounds accesses and use-after-scope bugs.