assert.h: Undefine ASSERT macro in case vendorcode headers set it

Some edk2 vendorcode headers define an ASSERT macro. They're guarded
with an #ifndef ASSERT, but if coreboot's assert.h gets included after
that header, we still have a problem. Add code to assert.h to undefine
any rogue definitions that may have already been set by vendorcode
headers.

This is ugly and should only be a stopgap... it would be nice if someone
maintaining those vendorcode parts could eventually replace it with a
better solution. One option would be to use a "guard header" for every
vendorcode header we want to pull into normal coreboot code which would
chain-include the vendorcode header and then undefine anything that
clashes with coreboot again.

Change-Id: Ibf8dc8b2365821e401ce69705df20aa7540aefb2
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32715
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/include/assert.h

@@ -19,6 +19,12 @@
 #include <arch/hlt.h>
 #include <console/console.h>
 
+/* TODO: Fix vendorcode headers to not define macros coreboot uses or to be more
+   properly isolated. */
+#ifdef ASSERT
+#undef ASSERT
+#endif
+
 /* GCC and CAR versions */
 #define ASSERT(x) {						\
 	if (!(x)) {						\