MFC r326315, r326330, r326331, r326412:
r326315:
Set DISTDIR and WRKDIRPREFIX when building ports within the chroot(8) to avoid mtime changes within the ports checkout, which can cause checksum differences.
r326330:
Add a comment to release/release.conf.sample documenting EMBEDDEDPORTS. [1] Remove and update stale documentation from release(7) while here.
r326331:
Correct a comment.
r326412:
Fix port build flags passed to make(1) after r326315, where it was missed for embedded image builds.
PR: 206344 [1]
Sponsored by: The FreeBSD Foundation