Avoid spaces in the productID / installation directory name.

The productID is used as the installation directory name, and
a space character within it can be problematic for some packaging
tools.  We therefore use a - instead.
Prepend $(DESTDIR) to install directories, for packaging tools.
Make sure the target dir exists before copying to it.

Parallel builds (make -j4) were failing because the installation directory
wasn't guaranteed to exist before we tried copying files to it.