* only support cmake for CLanguage in run_tests.py
* add support for run_tests.py build step environ
* switch C/C++ run_tests.py build to build_cxx script
* CLanguage cleanup
* build C# entirely with build_csharp script
* move entire PHP build to build_php.sh
* fixup C# build on linux and mac
* run_dep_checks Makefile target is deprecated
* get rid of the "makefile" logic in run_tests.py
* fixup C# build on linux and mac
* XML_REPORT env variable is useless for --use_docker runs
* add a TODO
* move "main" functionality towards end of run_tests.py
* use self.args instead of global
* yapf format
* remove the no longer useful --update_submodules features of run_tests.py
* fix check_epollexclusive check in run_tests.py