sync/atomic: fix data races in tests

Backport https://codereview.appspot.com/111320044 from Go
master library.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@217110 138bc75d-0d04-0410-961f-82ee72b054a4
	* go.test/go-test.exp: In +build lines, require whitespace around
	expected strings, fix check for negation.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@217111 138bc75d-0d04-0410-961f-82ee72b054a4
	* go.test/go-test.exp (go-set-goarch): Enable tests on s390[x].


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@217112 138bc75d-0d04-0410-961f-82ee72b054a4