linux: rebuild if previous failed due to internal compiler errors

Signed-off-by: Alejandro Mery <amery@geeks.cl>
linux: keep a $prefix.config.gz of the corresponding .config

Signed-off-by: Alejandro Mery <amery@geeks.cl>
linux: build arokux's sunxi-next-usb too

Signed-off-by: Alejandro Mery <amery@geeks.cl>