[FS#198] image: commit a16a8814ead80984ce4ef7bed756434119b3aafa breaks dnsmasq

[LEDE Bugs]

The following task is now closed:

FS#198 - image: commit a16a8814ead80984ce4ef7bed756434119b3aafa breaks dnsmasq
User who did this - Jo-Philipp Wich (jow-)

Reason for closing: Not a bug
Additional comments about closing: The issue is caused by the environment (unsuitable umask) and was exposed by the permission / rootfs generation rework. I added a umask build prereq check to fail the build straight away. This obviously won't help if there already cloned feeds with broken permissions but it will help new users to notify the problem early on.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=198