classes/archiver: run do_unpack_and_patch after do_preconfigure

The commit 8a7c7794 ("classes/archiver: Create patched archive before
configuring") fixed a race condition when using the archiver, but
introduced a bug where the GCC source would occasionally be deleted due
to the archiving code running before do_preconfigure. Instead, make sure
the archiving code runs after do_preconfigure by making
do_unpack_and_patch depend on it. This makes more sense anyway since
do_preconfigure is effectively an extension of do_patch.

This fixes errors like:

 cat: .../gcc/defaults.h: No such file or directory

when making certain configuration changes

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit d4be2640)
Signed-off-by: Steve Sakoman <steve@sakoman.com>