firefox: remove the separate-debug-info workaround

With the previous two commits, lld/LLVM stdenvs should now produce
`build-id`s that satisify `separate-debug-info.sh`

pkgs/applications/networking/browsers/firefox/common.nix

@@ -500,41 +500,6 @@ buildStdenv.mkDerivation ({
     gappsWrapperArgs+=(--argv0 "$out/bin/.${binaryName}-wrapped")
   '';
 
-  # Workaround: The separateDebugInfo hook skips artifacts whose build ID's length is not 40.
-  # But we got 16-length build ID here. The function body is mainly copied from pkgs/build-support/setup-hooks/separate-debug-info.sh
-  # Remove it when https://github.com/NixOS/nixpkgs/pull/146275 is merged.
-  preFixup = lib.optionalString enableDebugSymbols ''
-    _separateDebugInfo() {
-        [ -e "$prefix" ] || return 0
-
-        local dst="''${debug:-$out}"
-        if [ "$prefix" = "$dst" ]; then return 0; fi
-
-        dst="$dst/lib/debug/.build-id"
-
-        # Find executables and dynamic libraries.
-        local i
-        while IFS= read -r -d $'\0' i; do
-            if ! isELF "$i"; then continue; fi
-
-            # Extract the Build ID. FIXME: there's probably a cleaner way.
-            local id="$($READELF -n "$i" | sed 's/.*Build ID: \([0-9a-f]*\).*/\1/; t; d')"
-            if [[ -z "$id" ]]; then
-                echo "could not find build ID of $i, skipping" >&2
-                continue
-            fi
-
-            # Extract the debug info.
-            echo "separating debug info from $i (build ID $id)"
-            mkdir -p "$dst/''${id:0:2}"
-            $OBJCOPY --only-keep-debug "$i" "$dst/''${id:0:2}/''${id:2}.debug"
-
-            # Also a create a symlink <original-name>.debug.
-            ln -sfn ".build-id/''${id:0:2}/''${id:2}.debug" "$dst/../$(basename "$i")"
-        done < <(find "$prefix" -type f -print0)
-    }
-  '';
-
   postFixup = lib.optionalString crashreporterSupport ''
     patchelf --add-rpath "${lib.makeLibraryPath [ curl ]}" $out/lib/${binaryName}/crashreporter
   '';