Re-checking loader.rc file

Re-checking loader.rc file

The loader.rc file is now checked into the source, and is automatically updated
by python whenever the headers are updated so that it contains the version used
to build the loader.

If BUILD_DLL_VERSIONINFO is set in the command line, then the loader will use
that version to configure a new loader.rc and place it in the build directory.
Then it will use that loader.rc rather than the checked in file. This allows
Vulkan Runtimes to be built with an exact version.

The file is checked in to allow builds without modifying the source directory
and allowing GN builds to not need any additional configuration to work.