Support names like llvm-ar-3.4 and llvm-ranlib-3.4.

They are used in some packages. For example:
http://packages.ubuntu.com/saucy/i386/llvm-3.4/filelist

This fixes pr17721.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193612 91177308-0d34-0410-b5e6-96231b3b80d8