Makefile: allow top-level parallel build with BR2_PER_PACKAGE_DIRECTORIES=y

With per-package folder support, top-level parallel build becomes
safe, so we can enclose the .NOTPARALLEL statement in a
!BR2_PER_PACKAGE_DIRECTORIES condition.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
1 file changed