library.
Installs tblgen (required by Clang).
Translates handling of user settings and platform-dependant options to
its own file, where it can included by another project.
Installs the .cmake files required by projects like Clang.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124816 91177308-0d34-0410-b5e6-96231b3b80d8
