lib: Add ASan stub

Add a Kconfig option to enable address sanitizer on x86 architecture.
Create ASan dummy functions. And add relevant gcc flags to compile
ramstage with ASan.

Change-Id: I6d87e48b6786f02dd46ea74e702f294082fd8891
Signed-off-by: Harshit Sharma <harshitsharmajs@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42271
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>

src/lib/asan.c

@@ -0,0 +1,34 @@
+#include <stddef.h>
+
+#pragma GCC diagnostic ignored "-Wmissing-prototypes"
+
+#define DEFINE_ASAN_LOAD_STORE(size)                        \
+	void __asan_load##size(unsigned long addr)              \
+	{}                                                      \
+	void __asan_load##size##_noabort(unsigned long addr)    \
+	{}                                                      \
+	void __asan_store##size(unsigned long addr)             \
+	{}                                                      \
+	void __asan_store##size##_noabort(unsigned long addr)   \
+	{}
+
+DEFINE_ASAN_LOAD_STORE(1);
+DEFINE_ASAN_LOAD_STORE(2);
+DEFINE_ASAN_LOAD_STORE(4);
+DEFINE_ASAN_LOAD_STORE(8);
+DEFINE_ASAN_LOAD_STORE(16);
+
+void __asan_loadN(unsigned long addr, size_t size)
+{}
+
+void __asan_loadN_noabort(unsigned long addr, size_t size)
+{}
+
+void __asan_storeN(unsigned long addr, size_t size)
+{}
+
+void __asan_storeN_noabort(unsigned long addr, size_t size)
+{}
+
+void __asan_handle_no_return(void)
+{}