[CMake] Treating LLVM_INCLUDE_TOOLS, which is a bool, as a string to change behaviors...

[CMake] Treating LLVM_INCLUDE_TOOLS, which is a bool, as a string to change behaviors of the build is a dirty hack. We shouldn't do it.

Summary: I don't think anyone is relying on this behavior for bootstrapping (because I don't think it works), but if you do need it, speak now or forever hold your peace.

Reviewers: chapuni, samsonov

Reviewed By: samsonov

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10613

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240344 91177308-0d34-0410-b5e6-96231b3b80d8