shippable: build using all available cpus

As of this commit:

$ echo "container proc:" `getconf _NPROCESSORS_ONLN` `getconf _NPROCESSORS_CONF`
container proc: 2 2

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
1 file changed