patch qt6 to cross-compile qgnomeplatform & get gnome-style Qt theme

nixpatches/2023-03-03-qtbase-cross-compile.patch

@@ -0,0 +1,34 @@
+diff --git a/pkgs/development/libraries/qt-6/modules/qtbase.nix b/pkgs/development/libraries/qt-6/modules/qtbase.nix
+index e71b0a7613d..72779ac57a5 100644
+--- a/pkgs/development/libraries/qt-6/modules/qtbase.nix
++++ b/pkgs/development/libraries/qt-6/modules/qtbase.nix
+@@ -5,6 +5,7 @@
+ , version
+ , coreutils
+ , bison
++, buildPackages
+ , flex
+ , gdb
+ , gperf
+@@ -224,6 +225,8 @@ stdenv.mkDerivation rec {
+   ] ++ lib.optionals stdenv.isDarwin [
+     # error: 'path' is unavailable: introduced in macOS 10.15
+     "-DQT_FEATURE_cxx17_filesystem=OFF"
++  ] ++ lib.optionals (stdenv.buildPlatform != stdenv.hostPlatform) [
++    "-DQT_HOST_PATH=${buildPackages.qt6.full}"
+   ];
+ 
+   NIX_LDFLAGS = toString (lib.optionals stdenv.isDarwin [
+diff --git a/pkgs/development/libraries/qt-6/qtModule.nix b/pkgs/development/libraries/qt-6/qtModule.nix
+index 28180d3b0ca..f14c73b10ee 100644
+--- a/pkgs/development/libraries/qt-6/qtModule.nix
++++ b/pkgs/development/libraries/qt-6/qtModule.nix
+@@ -61,7 +61,7 @@ stdenv.mkDerivation (args // {
+       if [[ -z "$dontSyncQt" && -f sync.profile ]]; then
+         # FIXME: this probably breaks crosscompiling as it's not from nativeBuildInputs
+         # I don't know how to get /libexec from nativeBuildInputs to work, it's not under /bin
+-        ${lib.getDev self.qtbase}/libexec/syncqt.pl -version "''${version%%-*}"
++        perl ${lib.getDev self.qtbase}/libexec/syncqt.pl -version "''${version%%-*}"
+       fi
+     '';
+ 

nixpatches/list.nix

@@ -28,6 +28,10 @@
   # it's a revert of nixpkgs commit dcf630c172df2a9ecaa47c77f868211e61ae8e52
   ./2023-01-30-mesa-cma-leak.patch
 
+  # fix qt6.qtbase and qt6.qtModule to cross-compile.
+  # unfortunately there's some tangle that makes that difficult to do via the normal `override` facilities
+  ./2023-03-03-qtbase-cross-compile.patch
+
   # # kaiteki: init at 2022-09-03
   # vendorHash changes too frequently (might not be reproducible).
   # using local package defn until stabilized