makeModulesClosure: fixup firmware extraction

After a recent upgrade of modinfo, its output is now incorrect for
builtin modules. This commit filters out the output until a fix is made
available upstream

pkgs/build-support/kernel/modules-closure.sh

@@ -68,7 +68,17 @@ done
 
 mkdir -p $out/lib/firmware
 for module in $(cat closure); do
-    for i in $(modinfo -F firmware $module); do
+    # for builtin modules, modinfo will reply with a wrong output looking like:
+    #   $ modinfo -F firmware unix
+    #   name:           unix
+    #
+    # There is a pending attempt to fix this:
+    #   https://github.com/NixOS/nixpkgs/pull/96153
+    #   https://lore.kernel.org/linux-modules/20200823215433.j5gc5rnsmahpf43v@blumerang/T/#u
+    #
+    # For now, the workaround is just to filter out the extraneous lines out
+    # of its output.
+    for i in $(modinfo -F firmware $module | grep -v '^name:'); do
         mkdir -p "$out/lib/firmware/$(dirname "$i")"
         echo "firmware for $module: $i"
         cp "$firmware/lib/firmware/$i" "$out/lib/firmware/$i" 2>/dev/null || if test -z "$allowMissing"; then exit 1; fi