firefox: ensure pipewire is only enabled with wayland & webrtc

This ensures that we aren't applying any of the experiemental pipewire
patches when the dependencies aren't enabled. As of now pipewire only
works with wayland and webrtc. If either of them are not activated we
can't build with pipewireSupport and we should not.

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

@@ -21,8 +21,9 @@
 , pulseaudioSupport ? stdenv.isLinux, libpulseaudio
 , ffmpegSupport ? true
 , gtk3Support ? true, gtk2, gtk3, wrapGAppsHook
-, waylandSupport ? true, libxkbcommon, pipewire
+, waylandSupport ? true, libxkbcommon
 , gssSupport ? true, kerberos
+, pipewireSupport ? waylandSupport && webrtcSupport, pipewire
 
 ## privacy-related options
 
@@ -69,6 +70,7 @@
 }:
 
 assert stdenv.cc.libc or null != null;
+assert pipewireSupport -> !waylandSupport || !webrtcSupport -> throw "pipewireSupport requires both wayland and webrtc support.";
 
 let
   flag = tf: x: [(if tf then "--enable-${x}" else "--disable-${x}")];
@@ -84,6 +86,7 @@ let
   execdir = if stdenv.isDarwin
             then "/Applications/${binaryNameCapitalized}.app/Contents/MacOS"
             else "/bin";
+
 in
 
 stdenv.mkDerivation ({
@@ -94,12 +97,12 @@ stdenv.mkDerivation ({
 
   patches = [
     ./env_var_for_system_dir.patch
+  ] ++ lib.optional pipewireSupport
     (fetchpatch {
       # https://src.fedoraproject.org/rpms/firefox/blob/master/f/firefox-pipewire-0-3.patch
       url = "https://src.fedoraproject.org/rpms/firefox/raw/e99b683a352cf5b2c9ff198756859bae408b5d9d/f/firefox-pipewire-0-3.patch";
       sha256 = "0qc62di5823r7ly2lxkclzj9rhg2z7ms81igz44nv0fzv3dszdab";
     })
-  ]
   ++ patches;
 
 
@@ -128,7 +131,8 @@ stdenv.mkDerivation ({
   ++ lib.optional  pulseaudioSupport libpulseaudio # only headers are needed
   ++ lib.optional  gtk3Support gtk3
   ++ lib.optional  gssSupport kerberos
-  ++ lib.optionals waylandSupport [ libxkbcommon pipewire ]
+  ++ lib.optionals waylandSupport [ libxkbcommon ]
+  ++ lib.optionals pipewireSupport [ pipewire ]
   ++ lib.optionals stdenv.isDarwin [ CoreMedia ExceptionHandling Kerberos
                                      AVFoundation MediaToolbox CoreLocation
                                      Foundation libobjc AddressBook cups ];
@@ -142,8 +146,10 @@ stdenv.mkDerivation ({
 
   postPatch = ''
     rm -rf obj-x86_64-pc-linux-gnu
-
-    # needed for enabling webrtc+pipewire
+  '' + lib.optionalString pipewireSupport ''
+    # substitute the /usr/include/ lines for the libraries that pipewire provides.
+    # The patch we pick from fedora only contains the generated moz.build files
+    # which hardcode the dependency paths instead of running pkg_config.
     substituteInPlace \
       media/webrtc/trunk/webrtc/modules/desktop_capture/desktop_capture_generic_gn/moz.build \
       --replace /usr/include ${pipewire.dev}/include