libstdc++: Only use __builtin_sprintf if supported [PR 96083]

Clang doesn't support __builtin_sprintf, so use std::sprintf instead.

libstdc++-v3/ChangeLog:

	PR libstdc++/96083
	* include/ext/throw_allocator.h: Use __has_builtin to check for
	__builtin_sprintf support, and use std::sprtinf if necessary.