libstdc++: Link tests to libatomic as required [PR 97948]

libstdc++-v3/ChangeLog:

	PR libstdc++/97948
	* testsuite/29_atomics/atomic_float/wait_notify.cc: Add options
	for libatomic.
	* testsuite/29_atomics/atomic_integral/wait_notify.cc: Likewise.
	* testsuite/29_atomics/atomic_ref/wait_notify.cc: Likewise.

libstdc++-v3/testsuite/29_atomics/atomic_float/wait_notify.cc

@@ -2,6 +2,7 @@
 // { dg-do run { target c++2a } }
 // { dg-require-gthreads "" }
 // { dg-additional-options "-pthread" { target pthread } }
+// { dg-add-options libatomic }
 // { dg-skip-if "broken" { ! *-*-*linux } }
 
 // Copyright (C) 2020 Free Software Foundation, Inc.

libstdc++-v3/testsuite/29_atomics/atomic_integral/wait_notify.cc

@@ -2,6 +2,7 @@
 // { dg-do run { target c++2a } }
 // { dg-require-effective-target pthread }
 // { dg-require-gthreads "" }
+// { dg-add-options libatomic }
 
 // Copyright (C) 2020 Free Software Foundation, Inc.
 //

libstdc++-v3/testsuite/29_atomics/atomic_ref/wait_notify.cc

@@ -2,6 +2,7 @@
 // { dg-do run { target c++2a } }
 // { dg-require-effective-target pthread }
 // { dg-require-gthreads "" }
+// { dg-add-options libatomic }
 
 // Copyright (C) 2020 Free Software Foundation, Inc.
 //