During D12700 review I was asked to make configure installation consistent with CMake. Since I modeled implementation of Clang-format, I decided to fix problem in Clang-format make file too.
Just in case, possible improvements to configure (if it'll be around for awhile and somebody with more knowledge then me willing to do them):
- Make PROJ_sharedir in top-level Makefile.rules, since it's used for LLVM CMake modules and will be used for Clang-tidy.
- Since git-clang-format is Python script, it should be link from bin to share directory.