gcc-common/gcc-configure-common: Move gnu-configize to its own shared task

gcc-common/gcc-configure-common: Move gnu-configize to its own shared task

This command modifies ${S} and can race against other tasks running do_configure and
having the scripts disappear from under them. To avoid this move to its own
task and work on the shared work directory as a common task.

It needs to be a python task to avoid lots of shell exported variables as
dependencies.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>