llvm/test/CodeGen/X86/vector-gep.ll: Appease to add -mtriple=i686-linux.

This doesn't pass if stack alignment is not 16, like cygming, *bsd.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212334 91177308-0d34-0410-b5e6-96231b3b80d8