archiver.bbclass: Fix gcc-source corner case

archiver.bbclass: Fix gcc-source corner case

Bitbake couldn't add the task ar_configured when
trying to archive the configured source for
gcc-source-${PV} recipes. This is because the task
depended in the do_configure and this task doesn't
exist for gcc-source.

This fix allows to archive configured gcc-source recipe.

Signed-off-by: Mariano Lopez <mariano.lopez@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>