rootfs_postbuild: Run rauc_fixups here instead of in the makefile #5

Merged xogium merged 2 commits into LuminaSensum:stable-dev-board from LuminaSensum:WIP_rauc_fixup on 9 Aug 2020

2020-08-09	47e2054 Browse files » scripts/rauc_fixups.sh: Copy instead of symlinking ... This avoids race conditions during building by external modifications. Jookia committed on 9 Aug 2020
2020-08-09	7d73fae Browse files » external.mk: Fix rauc-fixups makefile race ... rauc-fixups would run after buildroot's targets, causing the image to fail. Instead have it run alongside other world targets. Jookia committed on 9 Aug 2020