Only run pacman -Rdd if we actually have something to uninstall

Author: kpcyrd

repro.in

@@ -269,7 +269,9 @@ __END__
         <(printf '%s\n' "${buildinfo_packages[@]}" | rev | cut -d- -f4- | rev | sort) \
         <(exec_nspawn build --bind="$(readlink -e ${cachedir}):/cache" pacman -Qq | sort))
 
-    exec_nspawn build pacman -Rdd --noconfirm -- $uninstall
+    if [ -n "$uninstall" ]; then
+        exec_nspawn build pacman -Rdd --noconfirm -- $uninstall
+    fi
 
     build_package "build" "$builddir"
     remove_snapshot "build"