opts: SANITIZE_ADDRESS wrongly cleared [PR108543]

opts: SANITIZE_ADDRESS wrongly cleared [PR108543]

Here we crash on a null fndecl ultimately because we haven't defined
the built-ins described in sanitizer.def.  So
builtin_decl_explicit (BUILT_IN_ASAN_POINTER_SUBTRACT);
returns NULL_TREE, causing an ICE later.

DEF_SANITIZER_BUILTIN only actually defines the built-ins when flag_sanitize
has SANITIZE_ADDRESS, or some of the other SANITIZE_*, but it doesn't check
SANITIZE_KERNEL_ADDRESS or SANITIZE_USER_ADDRESS.  Unfortunately, with
-fsanitize=address -fno-sanitize=kernel-address
or
-fsanitize=kernel-address -fno-sanitize=address
SANITIZE_ADDRESS ends up being unset from flag_sanitize even though
_USER/_KERNEL are set.  That's because -fsanitize=address means
SANITIZE_ADDRESS | SANITIZE_USER_ADDRESS and -fsanitize=kernel-address
is SANITIZE_ADDRESS | SANITIZE_KERNEL_ADDRESS but parse_sanitizer_options
does
  flags &= ~sanitizer_opts[i].flag;
so the subsequent -fno- unsets SANITIZE_ADDRESS.  Then no sanitizer
built-ins are actually defined.

I'm not sure why SANITIZE_ADDRESS isn't just SANITIZE_USER_ADDRESS |
SANITIZE_KERNEL_ADDRESS, I don't think we need 3 bits.

	PR middle-end/108543

gcc/ChangeLog:

	* opts.cc (parse_sanitizer_options): Don't always clear SANITIZE_ADDRESS
	if it was previously set.

gcc/testsuite/ChangeLog:

	* c-c++-common/asan/pointer-subtract-5.c: New test.
	* c-c++-common/asan/pointer-subtract-6.c: New test.
	* c-c++-common/asan/pointer-subtract-7.c: New test.
	* c-c++-common/asan/pointer-subtract-8.c: New test.