[autoconf] Fix m4 quoting for newer autotools

This simply fixes up quoting of macro invocations to appease newer versions of autotools.

http://llvm-reviews.chandlerc.com/D332



Signed-off-by: Saleem Abdulrasool <compnerd@compnerd.org>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173878 91177308-0d34-0410-b5e6-96231b3b80d8