allow build and localProduct to be in different directory trees
From Tom Junk:
Since our build nodes on DUNE are build-only-but-do-not-run, I was
wondering if we could put MRB_BUILDDIR
and the localProducts directories in different filesystems. That way,
we can speed the build if the build directory
is on a locally mounted disk, while the localProducts directory is in
NAS. The mrb reference guide seems to indicate
that that newDev will make the build and localProducts directories as
subdirectories of the same directory.
The solution: add -B and -P options to mrb newDev. This requires some rewriting of newDev.