Fix Android "in-the-source" build on Windows platform.

Reinstate back the logic to read CMake cache value for USE_MKLINK the proper way as the previous shortcut approach does not work as expected when user invokes cmake_clean.bat but leaving build dir as it is.
Clean up Engine library build script.
Convert additional cflags comments into accessible pkg-config's vars.

The additional flags are usually trivial on *nix platforms but they are not so on Windows platform for MSVC.
Refactor to expect log level parameter value after a space.

To be consistent with the rest of the Engine parameters.
Merge remote-tracking branch 'upstream/master'
SRGB update