I'm going to revise this request just a bit. lit actually isn't
necessary to include, because it can be trivially obtained with pip,
e.g. `pip install lit`. The necessary tools which should be included in
llvm-toolchain are at least FileCheck, not, and count. Some users may
also need yaml-bench.
Public bug reported:
The llvm-toolchain-3.8 change log reads in part:
"removed LLVM-internal tools (lit, FileCheck, not, *-tblgen, etc.);
not installed by CMake, not intended for distribution"
The "not intended for distribution" argument can easily be made for *-tblgen,
but a popular use
