Makefile.inc1: Avoid using release/Makefile for VERSION.

release/Makefile.inc1 has git executions that were being ran for each of
these lookups. The results were not needed so just lookup what we want
directly instead.

Reviewed by: gjb, rlibby, emaste (maybe)
Sponsored by: Dell EMC
Differential Revision: https://reviews.freebsd.org/D27643