Fix expand_builtin_atomic_fetch_op for pre-op (PR80902)

Fix expand_builtin_atomic_fetch_op for pre-op (PR80902)

__atomic_add_fetch adds a value to some memory, and returns the result.
If there is no direct support for this, expand_builtin_atomic_fetch_op
is asked to implement this as __atomic_fetch_add (which returns the
original value of the mem), followed by the addition.  Now, the
__atomic_add_fetch could have been a tail call, but we shouldn't
perform the __atomic_fetch_add as a tail call: following code would
not be executed, and in fact thrown away because there is a barrier
after tail calls.

This fixes it.

	PR middle-end/80902
	* builtins.c (expand_builtin_atomic_fetch_op): If emitting code after
	a call, force the call to not be a tail call.

From-SVN: r249603