Nix CI: split inputs and wlroots updating

Now there are separate update scripts for wlroots and for all other
inputs.

nix/update-wlroots.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env -S nix shell nixpkgs#gawk nixpkgs#git nixpkgs#gnused nixpkgs#jq nixpkgs#ripgrep -c bash
+
+# get wlroots revision from submodule
+SUB_REV=$(git submodule status | rg wlroots | awk '{ print substr($1,2)}')
+# and from lockfile
+CRT_REV=$(jq <flake.lock '.nodes.wlroots.locked.rev' -r)
+
+if [ "$SUB_REV" != "$CRT_REV" ]; then
+  echo "Updating wlroots..."
+  # update wlroots to submodule revision
+  nix flake lock --override-input wlroots "gitlab:wlroots/wlroots/$SUB_REV?host=gitlab.freedesktop.org"
+
+  # fix revision in wlroots.wrap
+  sed -Ei "s/[a-z0-9]{40}/$SUB_REV/g" subprojects/wlroots.wrap
+else
+  echo "wlroots is up to date!"
+fi