re PR go/89406 (Go testing leaves many temporary directories in /tmp around)

	PR go/89406
    go/internal/gccgoimporter: remove temporary directories in test
    
    Backport of https://golang.org/cl/164862.
    
    Updates https://gcc.gnu.org/PR89406
    
    Reviewed-on: https://go-review.googlesource.com/c/164863

From-SVN: r269338