[Test] Explictly pass target architecture.
[Test] Explictly pass target architecture.

If we're not being explicit, the test fails on windows.
Reported and tested by Aaron Ballman!


git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@235739 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld