main/busybox: backport proper pattern_list support for busybox grep

Closed Sören Tempel requested to merge nmeum/aports:busybox-pattern_list into master

Even though this patch was written by myself it was already included upstream. I find this issues to be particularly annoying as my mail client (community/mblaze) uses this feature and who known how long until busybox 1.32.0 is released.

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