Without this, running vcbuild repeatedly for some time will cause errors with msbuild saying the command line is too long (due to concatenation happening in vcvarsall).
Gyp will try a parallel build if it detect the system has >1 processor.
This functionality depends on the Python "multiprocessing" package. The
multiprocessing package on Windows requires that the top-level module is
importable as a module, see:
http://docs.python.org/2/library/multiprocessing.html#windows
This fixes issue #984.
gyp_uv was complaining because it never receives a value for which type
of library to build (static vs shared). This makes vcbuild.bat set the
default to build a static library.
