ninja is faster at building cmake packages than make, and according to reports
also more reliable at handling parallel builds
This commit includes a patch that adds GNU make jobserver support, in order to
allow more precise control over the number of parallel tasks

Enable parallel build by default for packages using ninja

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Rosen Penev <rosenp@gmail.com>