compressFirmwareXz: never compress lib/firmware/edid

this allows us not to pass `compressFirmware = false;`
 inside EDID derivations as this mechanic very tricky to discover.

related to NixOS#279789

pkgs/build-support/kernel/compress-firmware-xz.nix

@@ -7,14 +7,18 @@ let
 in
 
 runCommand "${firmware.name}-xz" args ''
+  edids=(-path 'lib/firmware/edid/*')
   mkdir -p $out/lib
   (cd ${firmware} && find lib/firmware -type d -print0) |
-      (cd $out && xargs -0 mkdir -v --)
-  (cd ${firmware} && find lib/firmware -type f -print0) |
+      (cd $out && xargs -0 mkdir -pv --)
+  (cd ${firmware} && find lib/firmware -type f -not "''${edids[@]}" -print0) |
       (cd $out && xargs -0rtP "$NIX_BUILD_CORES" -n1 \
           sh -c 'xz -9c -T1 -C crc32 --lzma2=dict=2MiB "${firmware}/$1" > "$1.xz"' --)
-  (cd ${firmware} && find lib/firmware -type l) | while read link; do
+  (cd ${firmware} && find lib/firmware -type l -not "''${edids[@]}") | while read link; do
       target="$(readlink "${firmware}/$link")"
       ln -vs -- "''${target/^${firmware}/$out}.xz" "$out/$link.xz"
   done
+  (cd ${firmware} && find lib/firmware -type f "''${edids[@]}" -print0) |
+      (cd $out && xargs -0rtP "$NIX_BUILD_CORES" -n1 \
+          sh -c 'ln -vs -- "${firmware}/$1" "$out/$1"' --)
 ''

pkgs/tools/misc/edid-generator/default.nix

@@ -21,9 +21,6 @@ stdenv.mkDerivation {
   pname = "edid-generator";
   version = "master-2023-11-20";
 
-  # so `hardware.firmware` doesn't compress it
-  compressFirmware = false;
-
   src = fetchFromGitHub {
     owner = "akatrevorjay";
     repo = "edid-generator";