Revert "[Driver] Remove unneeded *-linux-gnu after D158183"

This broke several buildbots:
https://lab.llvm.org/buildbot/#/builders/193
https://lab.llvm.org/buildbot/#/builders/259
https://lab.llvm.org/staging/#/builders/185
https://lab.llvm.org/staging/#/builders/140

This reverts commit 435ea21c.