handle project downloads in main lbmk script

this means the unified /tmp handling is now provided for
in both the former "fetch" and "fetch_trees" script, which
are now (respectively):

./update project repo
./update project trees

if the fetch scripts weren't cleaning /tmp before, they
now are, because lbmk handles it

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

script/build/grub/utils

@@ -27,7 +27,7 @@ set -u -e
 main()
 {
 	printf "Building GRUB\n"
-	[ -d "grub/" ] || ./fetch grub || err "cannot fetch grub"
+	[ -d "grub/" ] || ./update project repo grub || err "cannot fetch grub"
 	build_grub
 }