Revert "runtime: temporarily disable stack barriers on sparc64"
Revert "runtime: temporarily disable stack barriers on sparc64"

This reverts commit c137922c8d24a9fd7155bf177887bdaac81aa156.

Causes regressions in some tests even though others passed afterwards.

4ad/go,4ad/go,4ad/go,4ad/go,4ad/go,4ad/go,4ad/go,4ad/go