WIP provide a builddep cache

Author: ydirson

src/xcp_ng_dev/cli.py

@@ -117,6 +117,10 @@ def buildparser():
     parser_build.add_argument(
         '--rpmbuild-stage', action='store',
         help=f"Request given -bX stage rpmbuild, X in [{RPMBUILD_STAGES}]")
+    parser_build.add_argument(
+        '--builddep-dir',
+        help="Directory where the build-dependency RPMs will be cached. "
+             "The directory is created if it doesn't exist")
     add_container_args(parser_build)
     add_common_args(parser_build)