Fix for 64Bit builds with VC from command line

Previously builds for 64 Bit targets on the x64 Native Tools Command
Prompt failed while trying to link the 64Bit build godot objects with
32Bit vc libraries. This was due to wrong library directories.

Since there are the environment variables INCLUDE and LIB which are
containing the correct paths this patch uses those now to fix the linking
issue.

Signed-off-by: Vinzenz Feenstra <evilissimo@gmail.com>