xvfb: promote to proper package

This can (and should!) be used by more than just xvfb-run.

pkgs/servers/x11/xorg/overrides.nix

@@ -905,6 +905,33 @@ self: super:
         };
       }));
 
+  # xvfb is used by a bunch of things to run tests
+  # and doesn't support hardware accelerated rendering
+  # so remove it from the rebuild heavy path for mesa
+  xvfb = super.xorgserver.overrideAttrs(old: {
+    configureFlags = [
+      "--enable-xvfb"
+      "--disable-xorg"
+      "--disable-xquartz"
+      "--disable-xwayland"
+      "--disable-glamor"
+      "--disable-glx"
+      "--disable-dri"
+      "--disable-dri2"
+      "--disable-dri3"
+      "--with-xkb-bin-directory=${xorg.xkbcomp}/bin"
+      "--with-xkb-path=${xorg.xkeyboardconfig}/share/X11/xkb"
+      "--with-xkb-output=$out/share/X11/xkb/compiled"
+    ];
+
+    buildInputs = old.buildInputs ++ (with xorg; [
+      pixman
+      libXfont2
+      xtrans
+      libxcvt
+    ]);
+  });
+
   lndir = super.lndir.overrideAttrs (attrs: {
     buildInputs = [];
     nativeBuildInputs = [ updateAutotoolsGnuConfigScriptsHook ];

pkgs/tools/misc/xvfb-run/default.nix

@@ -2,7 +2,7 @@
 , stdenvNoCC
 , fetchFromGitHub
 , makeWrapper
-, xorgserver
+, xorg
 , getopt
 , xauth
 , util-linux
@@ -39,7 +39,7 @@ stdenvNoCC.mkDerivation rec {
     patchShebangs $out/bin/xvfb-run
     wrapProgram $out/bin/xvfb-run \
       --set-default FONTCONFIG_FILE "${fontsConf}" \
-      --prefix PATH : ${lib.makeBinPath [ getopt xorgserver xauth which util-linux gawk coreutils ]}
+      --prefix PATH : ${lib.makeBinPath [ getopt xorg.xvfb xauth which util-linux gawk coreutils ]}
   '';
 
   doInstallCheck = true;

pkgs/top-level/all-packages.nix

@@ -14659,20 +14659,6 @@ with pkgs;
 
   xvfb-run = callPackage ../tools/misc/xvfb-run {
     inherit (texFunctions) fontsConf;
-
-    # xvfb-run is used by a bunch of things to run tests
-    # and doesn't support hardware accelerated rendering
-    # so remove it from the rebuild heavy path for mesa
-    xorgserver = xorg.xorgserver.overrideAttrs(old: {
-      buildInputs = lib.filter (pkg: lib.getName pkg != "mesa") old.buildInputs;
-      configureFlags = old.configureFlags ++ [
-        "--disable-glamor"
-        "--disable-glx"
-        "--disable-dri"
-        "--disable-dri2"
-        "--disable-dri3"
-      ];
-    });
   };
 
   xvkbd = callPackage ../tools/X11/xvkbd { };