Tidy up this line of the Makefile before I start hacking on it.

I really should sort it or do something more sustainable, but I couldn't
work up the energy to do it... Sorry.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191832 91177308-0d34-0410-b5e6-96231b3b80d8