ubsan: entirely disable alignment checks under UBSAN_TRAP

Commit 8d58f222 ("ubsan: disable UBSAN_ALIGNMENT under
COMPILE_TEST") tried to fix the pathological results of UBSAN_ALIGNMENT
with UBSAN_TRAP (which objtool would rightly scream about), but it made
an assumption about how COMPILE_TEST gets set (it is not set for
randconfig).  As a result, we need a bigger hammer here: just don't
allow the alignment checks with the trap mode.

Fixes: 8d58f222 ("ubsan: disable UBSAN_ALIGNMENT under COMPILE_TEST")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Elena Petrova <lenaptr@google.com>
Link: http://lkml.kernel.org/r/202005291236.000FCB6@keescook
Link: https://lore.kernel.org/lkml/742521db-1e8c-0d7a-1ed4-a908894fb497@infradead.org/Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/Kconfig.ubsan

@@ -63,7 +63,7 @@ config UBSAN_SANITIZE_ALL
 config UBSAN_ALIGNMENT
 	bool "Enable checks for pointers alignment"
 	default !HAVE_EFFICIENT_UNALIGNED_ACCESS
-	depends on !X86 || !COMPILE_TEST
+	depends on !UBSAN_TRAP
 	help
 	  This option enables the check of unaligned memory accesses.
 	  Enabling this option on architectures that support unaligned