testsdk.bbclass: set PREMIRRORS for kernel to speed up test
Currently if we do a testsdkext task for the image, it would take
very long time to finish. The time is mostly spent fetching kernel
source via network.
We have done some configuration in auto.conf, trying to make use
of own-mirrors.bbclass to avoid fetching kernel via network.
However, the solution normally does not work. Below is some log
from log.do_fetch.
The tar.gz file is not available. It is generated only if
BB_GENERATE_MIRROR_TARBALLS is set to "1". The default value of
BB_GENERATE_MIRROR_TARBALLS is "0", and according to the manual, users
need choose to set it to "1" only if they are trying to make a source
mirror. So generally, this var's value is "0".
Anyway, we do need to avoid fetching kernel source from network when
doing testsdkext. So set PREMIRRORS in auto.conf to achieve this.
After this change, the time reduces from 4209.131s to 1399.436s on
my local machine.
[YOCTO #12729]
Signed-off-by: Chen Qi <Qi.Chen@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
