sanitizer: Cherry-pick realpath fix

sanitizer: Cherry-pick realpath fix

tsan in some cases starts ignoring interceptors and only calls the
intercepted functions.  But for realpath the behavior for NULL second argument
was only handled in the interceptor and intercepted function was the one
found by dlsym which is often one that doesn't handle NULL as second argument.

Fixed by using dlvsym with "GLIBC_2.3" if possible for intercepted function
and don't emulate behavior in the wrapper.

2021-08-11  Jakub Jelinek  <jakub@redhat.com>

	* sanitizer_common/sanitizer_common_interceptors.inc: Cherry-pick
	llvm-project revision faef0d042f523357fe5590e7cb6a8391cf0351a8.