require all makefiles to have the 'builddep-opamfiles' target

prepare-opam.sh

@@ -49,16 +49,7 @@ opam repo prio iris-dev 1 # make sure this stays at the top
 echo
 
 # Make sure the the builddep package(s) exist and are up-to-date.
-if test -f opam; then
-    # Old-style package: a single opam file
-    make build-dep/opam
-    # Copy it to new-style location
-    mkdir -p builddep
-    cp build-dep/opam builddep/opam
-else
-    # New-style package has a dedicated target to just generate the files
-    make builddep-opamfiles
-fi
+make builddep-opamfiles
 
 # Update old opam, if we got a cache.
 if [[ -z "$FRESH_OPAM" ]]; then # skip if this is a fresh opam root