archiver.bbclass: various fixes for original+diff mode
The diff.gz gets created in do_unpack_and_patch, but
do_deploy_archives did not depend on it, so there was a race
condition. For example, "bitbake linux-intel:do_deploy_archives"
without a prior "bitbake linux-intel:do_kernel_configme" did not
deploy the diff.gz.
When do_unpack_and_patch ran first, it failed because the output
directory didn't exist yet and the error was not detected because the
result of the diff command wasn't checked.
Changing the current working directory in create_diff_gz() without
returning to the original directory caused warnings like this:
WARNING: linux-intel-... do_unpack_and_patch: Task do_unpack_and_patch changed cwd to .../tmp-glibc/work-shared/intel-corei7-64
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
