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/handle/make/file

@@ -52,7 +52,7 @@ main()
 
 handle_dependencies()
 {
-	[ -d "${project}" ] || ./fetch "${project%/*}" || \
+	[ -d "${project}" ] || ./update project repo "${project%/*}" || \
 	    err "handle_dependencies: can't fetch ${project%/*}"
 	[ -d "${project}" ] || \
 		err "handle_dependencies: ${project%/*} not downloaded"