Shared work directory proof of concept

One of the items on the 1.1 feature list is sharing work directories. This is desirable for example for gcc where the same sources are unpacked and patched for gcc-cross-initial, gcc-cross-intermediate, gcc-cross, gcc-runtime and so on.

I've done a little experimentation with this and the code linked to below shows its at least possible and the kind of changes we might need to make to bitbake to support it:

http://git.yoctoproject.org/cgit.cgi/poky-contrib/commit/?h=rpurdie/gcc-sharedwork&id=4a22c2212466ef3bcb20960b1f99f8509347b24d

There are at least 4 issues I've noted in the commit which we'd need to to look before we could start using this code, nothing impossible though, just needs more work.

Cheers,

Richard