Summary:
This can be used for distinguishing between cmake and autoconf builds.
Users may need this in order to handle inconsistencies between the
outputs of the two build systems.
Reviewers: echristo, chandlerc, beanz
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D11838
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247159 91177308-0d34-0410-b5e6-96231b3b80d8