devcontainer: run container with privileges

Needed to actually execute osbuild in the container, since it
needs to mount and access loop devices.

.devcontainer/devcontainer.json

@@ -4,8 +4,14 @@
     "dockerfile": "Dockerfile",
     "context": ".."
   },
+  "mounts": [
+    "source=osbuild-share,target=/root/.local/share,type=volume"
+  ],
+  "runArgs": [
+    "--privileged"
+  ],
   "extensions": [
     "laurenttreguier.rpm-spec",
     "golang.Go"
   ]
-}
+}