libstdc++: Disable atomic wait for freestanding [PR105021]

libstdc++: Disable atomic wait for freestanding [PR105021]

We use either condition variables or futexes to implement atomic waits,
so we can't do it in freestanding. This is non-conforming, so should be
revisited later, probably by making freestanding atomic waiting
operations spin without ever blocking.

Reviewed-by: Thomas Rodgers <trodgers@redhat.com>
libstdc++-v3/ChangeLog:

	PR libstdc++/105021
	* include/bits/atomic_base.h [!_GLIBCXX_HOSTED]: Do not include
	<bits/atomic_wait.h> for freestanding.

(cherry picked from commit 5bf59b004808abf6acbfe5ef54a0f9216b8dce22)