Add support to config.setcpv() for caching USE settings from built
packages, and use it for evaluating conditional USE deps in atoms
passed via IPC to helpers like has_version and best_version.
Since the pickled object that contains the IPC command will no longer
contain USE, it should solve cases that have been reported in which
large USE strings trigger poor handling of non-blocking read in
pickle.load():
Traceback (most recent call last):
File "/usr/bin/emerge", line 43, in <module>
retval = emerge_main()
File "/usr/lib64/portage/pym/_emerge/main.py", line 1649, in emerge_main
myopts, myaction, myfiles, spinner)
File "/usr/lib64/portage/pym/_emerge/actions.py", line 437, in action_build
retval = mergetask.merge()
File "/usr/lib64/portage/pym/_emerge/Scheduler.py", line 1033, in merge
rval = self._merge()
File "/usr/lib64/portage/pym/_emerge/Scheduler.py", line 1349, in _merge
self._main_loop()
File "/usr/lib64/portage/pym/_emerge/Scheduler.py", line 1498, in _main_loop
self._poll_loop()
File "/usr/lib64/portage/pym/_emerge/PollScheduler.py", line 139, in _poll_loop
handler(f, event)
File "/usr/lib64/portage/pym/_emerge/EbuildIpcDaemon.py", line 36, in _input_handler
obj = pickle.load(self._files.pipe_in)
File "/usr/lib64/python2.6/pickle.py", line 1370, in load
return Unpickler(file).load()
File "/usr/lib64/python2.6/pickle.py", line 858, in load
dispatch[key](self)
File "/usr/lib64/python2.6/pickle.py", line 1195, in load_setitem
value = stack.pop()
IndexError: pop from empty list
4 files changed
