Add missing -target triple to ELF tests.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@221505 91177308-0d34-0410-b5e6-96231b3b80d8
Disable a Mach-O test on Windows that depends on Unix path separator.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@221506 91177308-0d34-0410-b5e6-96231b3b80d8