mk: Download vendorfiles before building release

Do it just after creating the src archive. This way,
everything is downloaded all at once.

Otherwise, a momentary lapse of internet uptime will
cause a release build to fail later on, and one of
lbmk's flaws is that this would then mean you must
re-build from scratch.

If we assume that the internet is working within a
short period of time, then this change would mitigate
that possibility. If something did happen during tar
archive creation, that's a much shorter amount of time
that is "wasted".

Signed-off-by: Leah Rowe <leah@libreboot.org>

mk

@@ -85,6 +85,7 @@ build_release()
 	touch "$srcdir/lock" || $err "can't make lock file in $srcdir/"
 	(
 	cd "$srcdir" || $err "$vdir: 2 !cd \"$srcdir\""
+	x_ ./mk -d coreboot
 	mk -b coreboot pico-serprog stm32-vserprog pcsx-redux
 	x_ mv bin ../roms
 	) || $err "can't build rom images"