sstate.bbclass: Detect overwriting files in sstate controlled directories
We have a potential problem where two sstate packages try and touch the same
file. This adds code which will print a warning whenever this happens.
The implementation does but by maintaining a master file list and comparing
file accesses against this. There are a number of places we have duplicate
accesses which are harmless, mostly in the deploy directory so these
are whitelisted.
For now the code prints warnings, this could be strengthened in future to
become error messages. Whilst working on this code on and off over the past
few months various issues were uncovered, some serious.
[YOCTO #238]
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
