c++: don't use strchrnul [PR107781]

The contracts implementation was using strchrnul, which is a glibc
extension, so bootstrap broke on non-glibc targets.  Use C89 strcspn
instead.

	PR c++/107781

gcc/cp/ChangeLog:

	* contracts.cc (role_name_equal): Use strcspn instead
	of strchrnul.
1 file changed