Add the .NOTPARALLEL target to each local Makefile command-line
interface entry point file so that even with -j we launch only
one "make -f Makefile2" at a time.  The actual build rules
in Makefile2 and lower will still run in parallel.

Do not add .NOTPARALLEL for Borland or Watcom make tools because
they do not tolerate it.  Other make tools that do not understand
.NOTPARALLEL will not be hurt.

Suggested-by: Robert Luberda <robert-cmake@debian.org>