Windows: Native build failed due to missing gnulib dependencies

Windows: Native build failed due to missing gnulib dependencies

The windows build failed because the gnulib header files were not
build before the compilation of c files for the native build.
The gnulib headers are
listed in the BUILT_SOURCES but that must be the first dependency
before the object files belonging to the executable. This is the
case for the default make target but not for an individual
executable like src/ui/terminal/pspp. I adapted the make file
to use the default make target.
See: https://www.gnu.org/software/automake/manual/html_node/Sources.html