Add support for Undefined Behavior Sanitizer

Initial support for undefined behavior sanitizer in ramstage. Enabling
this will add -fsanitize=undefined to the compiler command line and
link with ubsan.c in ramstage. Code with UB triggers a report with
error, file, and line number, then aborts.

Change-Id: Ib139a418db97b533f99fc59bcb1a71fb6dcd01d8
Signed-off-by: Ryan Salsamendi <rsalsamendi@hotmail.com>
Reviewed-on: https://review.coreboot.org/20156
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>

src/lib/Makefile.inc

@@ -15,6 +15,10 @@
 subdirs-y += loaders
 subdirs-y += gnat
 
+ifeq ($(CONFIG_UBSAN),y)
+ramstage-y += ubsan.c
+CFLAGS_ramstage += -fsanitize=undefined
+endif
 
 ifneq ($(CONFIG_BOOTBLOCK_CUSTOM),y)
 bootblock-y += bootblock.c