PC-BSD/trueos 6ddc0bbtools/build beinstall.sh

Update beinstall to use the mergemaster/etcupdate from the source tree instead
of the installed one.

Approved by:    will (mentor)
Differential Revision:  https://reviews.freebsd.org/D20291
DeltaFile
+10-11tools/build/beinstall.sh
+10-111 files

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