Allow Unsupported platforms to run, when Environment variables are set.
Allow Unsupported platforms to run, when Environment variables are set.

Move platform check and Error into resolveEmbeddedGitDir, so if the
Environment variable 'LOCAL_GIT_DIRECTORY' is set, Unsupported platforms
are still able to run.

Change path.join to set git-core and git to be if win32 else 'others'

desktop/dugite,desktop/dugite,desktop/dugite