CMakeLists: refactor to optionally use native libs #1633

Job	Run time
validate_python / Validate Python Code	1m 41s
validate_imported_protos / Validate Imported Proto Files	17s
create_client_artifacts / Windows Artifacts	1m 42s
cancel_builds / Cancel Build(s)	4s
create_client_artifacts / Linux Artifacts	28s
build_nilrt / NILRT Cross Compile with GCC 6.3.0	14m 5s
build_desktop / Windows Build	1h 41m 41s
build_desktop / Ubuntu Build	1h 7m 19s
run_ubuntu_system_tests	0s
run_win_system_tests	0s
create_release	0s
	3h 7m 17s

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