Provide a friendly error message if someone tries to use the CMake build without invoking the ``contrib/cmake/boostrap.py`` script.
Provide a friendly error message if someone tries to use the CMake
build without invoking the ``contrib/cmake/boostrap.py`` script.

kyledewey/z3,kyledewey/z3,mschlaipfer/z3,seahorn/z3,kyledewey/z3,kyledewey/z3,seahorn/z3,mschlaipfer/z3,seahorn/z3,mschlaipfer/z3,seahorn/z3,mschlaipfer/z3,mschlaipfer/z3,kyledewey/z3,mschlaipfer/z3,seahorn/z3,seahorn/z3,kyledewey/z3