Projects for Gn learning. by liangkz.

2021.04.20 add "GnHelloWorld".
	init project, build only "executable".

2021.04.21 add "GnHW_libs"
	base on "GnHelloWorld", add and build "static_library" & "shared_library".

2021.04.22 add "GnHW_libs_tc"
	base on "GnHW_libs", add config and gcc toolchain.