hack: add separate function to create common container engine args

Add a separate function to create common container engine arguments
to reduce complexity in container_build function.

Signed-off-by: Alexander Bachmann <[email protected]>

hack/build-image

@@ -219,17 +219,25 @@ def container_build(cli, target):
         # --arch is not provided. So if the target arch and the host_arch
         # are the same, skip passing the extra argument.
         args.append(f"--arch={target.arch}")
+    run(cli, args + create_common_container_engine_args(cli, target), check=True)
+
+def create_common_container_engine_args(cli, target):
+    args = []
+    pkgs_from = PACKAGES_FROM[target.pkg_source]
+    if pkgs_from:
+        args.append(f"--build-arg=INSTALL_PACKAGES_FROM={pkgs_from}")
+
     if cli.extra_build_arg:
         args.extend(cli.extra_build_arg)
+
     for tname in target.all_names(baseless=cli.without_repo_bases):
         args.append("-t")
         args.append(tname)
+
     args.append("-f")
     args.append(target_containerfile(target))
     args.append(kind_source_dir(target.name))
-    args = [str(a) for a in args]
-    run(cli, args, check=True)
-
+    return [str(a) for a in args]
 
 def container_push(cli, push_name):
     """Construct and execute a command to push a container image."""