bob: colliding workdirs?

[Greg Troxel <gdt%lexort.com@localhost>]

I'm doing builds on multiple machines, and have noticed enough of a
trend to feel it's ok to ask about it.

My builds are building both py313 and py314, due to a bob
bug/missing-feature of not being able to specify the wanted versions
when foo/py-bar appears in pkgpaths.*

In multiple builds, I have had a bunch of failures, pyN-foo when the
build was wanting to build both py313-foo and py314-foo.  Doing "bob
rebuild --all" they build ok, and logs make it look like a working
directory collision.  Building in tmfps, sandboxes are separate, but if
building on "disk", they appear to all end up in the same place.

(There's likely an unrelated problem where tmpfs isn't used, for tiny
things, but that's an orthogonal issue I think.)


So, I think bob either needs:

   - locking of a pkgpath that uses "disk" against simultaneous builds
     of multi-version programs, or
   - per-sandbox subdirs in the disk tmp

but I also think it's reasonably likely I'm off here.

*I want only the default pyversion, like make package would get you,
unless the package is coded not to accept that, in which case I want
what the package would choose if I typed make package, and obviously
dependencies should all work like they do not under bob -- but this
message is about something else.  (My impression is that this is
supported in pbulk.)