[mips] Add support for the new mips-mti-linux toolchain.

The original commit in r249137 added the mips-mti-linux toolchain. However,
the newly added tests of that commit failed in few buildbots. This commit
re-applies the original changes but XFAILs the test file which caused
the buildbot failures. This will allow us to examine what's going wrong
without having to commit/revert large changes.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@251633 91177308-0d34-0410-b5e6-96231b3b80d8