Fix agent copy during release

If there isn't a lib dir yet it'll copy as lib instead of getting put
inside the directory.

ci/build/build-release.sh

@@ -59,6 +59,7 @@ EOF
 
   if [ "$KEEP_MODULES" = 1 ]; then
     rsync node_modules/ "$RELEASE_PATH/node_modules"
+    mkdir -p "$RELEASE_PATH/lib"
     rsync ./lib/coder-cloud-agent "$RELEASE_PATH/lib"
   fi
 }