A faster bootfast

[Nick Roberts]

On my PC "make bootfast" doesn't live up to its name and is not all that fast.
mostlyclean is updated twice: firstly through bootstrap-clean-before-fast and
secondly through bootstrap-build:


bootstrap-build: FRC
        (cd lisp; $(MAKE) $(MFLAGS) bootstrap-prepare)
        (cd src; $(MAKE) $(MFLAGS) bootstrap)
        (cd lisp; $(MAKE) $(MFLAGS) bootstrap 
EMACS=../src/bootstrap-emacs${EXEEXT})
        (cd src; $(MAKE) $(MFLAGS) mostlyclean)
        $(MAKE) $(MFLAGS) all
        (cd lisp; $(MAKE) $(MFLAGS) bootstrap-after)

It appears that the C source files in src theat get built the first time
(cd src; $(MAKE) $(MFLAGS) bootstrap) only to be deleted by 
(cd src; $(MAKE) $(MFLAGS) mostlyclean) are identical to those that are
built by $(MAKE) $(MFLAGS) all. I think others may be identical also
i.e temac, prefix-args, libXMenu11.a, liblw.a, DOC, buildobj.lst

Could the list of files deleted on the second mostlyclean be reduced to speed
things up?  e.g to just bootstrap-emacs

Nick