Without this I see a number of tests failing when -m32 is used.

libstdc++-v3/ChangeLog:

	* testsuite/lib/dg-options.exp (add_options_for_libatomic): Also
	add libatomic options for 32-bit sparc*-*-linux-gnu.

Eric, are you OK with this? It adds -latomic and the appropriate -L
options to tests that use { dg-add-options libatomic }, because
sparcv8 needs libatomic for some std::atomic ops.