Fix build.py path to find Windows Python.
Fix build.py path to find Windows Python.

Replace --cmake and --ninja with --path.

On Cygwin, escape to native Windows.

antiagainst/shaderc,AWoloszyn/shaderc,antiagainst/shaderc,antiagainst/shaderc,fuchsia-mirror/third_party-shaderc,dneto0/shaderc,fuchsia-mirror/third_party-shaderc,fuchsia-mirror/third_party-shaderc,AWoloszyn/shaderc,antiagainst/shaderc,dneto0/shaderc,dneto0/shaderc,dneto0/shaderc,AWoloszyn/shaderc