Re: (toplevel) Fix dramatic breakage for ordinary crosses (related to program_transform_name)

[DJ Delorie <dj@delorie.com>]

> Unless...  We could perhaps have NOTPARALLEL set by default, which
> would take care of avoiding configurations in parallel even without
> serialized dependencies, but a configure option to disable NOTPARALLEL
> and introduce locking.  DJ, how does this sound for you?

I am not "vehemently" opposed to it.  I've just seen, through
experience, that there are lots of ways for it to go wrong.
Serialized dependencies is a lot simpler and less error-prone (once we
get them right, nobody's commented on my last suggestion).  If we had
a simple locking mechanism that worked on all the
ext/nfs/dos/samba/etc/distcc filesystems we need to support, I'd be OK
with it.  I just think that people underestimate how much effort it
takes to do locking reliably.

The problem with NOTPARALLEL is that it shuts of *ALL* the toplevel
parallelisms, including building A while configuring B, and testing in
parallel.  The toplevel Makefile really needs to allow parallel jobs
to take advantage of the work we've done.  We just need to be able to
identify the parts that can't be done simultaneously, and somehow
prevent those.