Fix parallel build and bootstrap on MS-Windows.

Fix parallel build and bootstrap on MS-Windows.

 nt/makefile.w32-in: (all): Don't depend on stamp_BLD and on maybe-bootstrap.
 (all-other-dirs-$(MAKETYPE)): Depend on maybe-bootstrap.
 (bootstrap-gmake): Invoke the "clean" and build targets in 2
 separate commands, so they run in that order even under "make -j".
 lib/makefile.w32-in (gnulib, all): Don't depend on stamp_BLD.
 lib-src/makefile.w32-in (ALL): Now the list of executables, not of phony
 targets.
 (.PHONY): Only make-docfile is its prerequisite now.
 (make-docfile): Don't depend on stamp_BLD.  Add a comment about
 the need in this target.
 (ctags, etags, ebrowse, hexl, movemail, emacsclient)
 (test-distrib): Phony targets removed.
 ($(BLD)/test-distrib.exe): Run test-distrib as part of the recipe.
 (all): Don't depend on stamp_BLD.