qt58.qtbase: Fix path to fallback libGL

pkgs/development/libraries/qt-5/5.8/qtbase/default.nix

@@ -40,7 +40,7 @@ stdenv.mkDerivation {
     copyPathsToStore (lib.readPathsFromFile ./. ./series)
     ++ [(if stdenv.isDarwin then ./cmake-paths-darwin.patch else ./cmake-paths.patch)]
     ++ lib.optional decryptSslTraffic ./decrypt-ssl-traffic.patch
-    ++ lib.optionals mesaSupported [ ./dlopen-gl.patch ./mkspecs-libgl.patch ];
+    ++ lib.optionals mesaSupported [ ./mkspecs-libgl.patch ];
 
   postPatch =
     ''
@@ -54,9 +54,6 @@ stdenv.mkDerivation {
       sed -i 's/PATHS.*NO_DEFAULT_PATH//' "mkspecs/features/data/cmake/Qt5BasicConfig.cmake.in"
     ''
     + lib.optionalString mesaSupported ''
-      substituteInPlace \
-        src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp \
-        --replace "@mesa_lib@" "${mesa.out}"
       substituteInPlace mkspecs/common/linux.conf \
         --replace "@mesa_lib@" "${mesa.out}" \
         --replace "@mesa_inc@" "${mesa.dev or mesa}"
@@ -223,6 +220,8 @@ stdenv.mkDerivation {
         then ''-DNIXPKGS_LIBDBUS="${dbus.lib}/lib/libdbus-1"''
         else ''-DNIXPKGS_LIBDBUS=""'')
     ]
+    ++ lib.optional mesaSupported
+       ''-DNIXPKGS_MESA_GL="${mesa.out}/lib/libGL"''
     ++ lib.optionals stdenv.isDarwin
     [
       "-D__MAC_OS_X_VERSION_MAX_ALLOWED=1090"

pkgs/development/libraries/qt-5/5.8/qtbase/dlopen-gl.patch

@@ -1,17 +1,19 @@
-Index: qtbase-opensource-src-5.5.1/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
+Index: qtbase-opensource-src-5.8.0/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
 ===================================================================
---- qtbase-opensource-src-5.5.1.orig/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
+--- qtbase-opensource-src-5.8.0.orig/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
-+++ qtbase-opensource-src-5.5.1/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
++++ qtbase-opensource-src-5.8.0/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
-@@ -563,7 +563,12 @@ void (*QGLXContext::getProcAddress(const
+@@ -576,7 +576,14 @@ QFunctionPointer QGLXContext::getProcAdd
-             {
+ #ifndef QT_NO_LIBRARY
                  extern const QString qt_gl_library_name();
  //                QLibrary lib(qt_gl_library_name());
 +                // Check system library paths first
                  QLibrary lib(QLatin1String("GL"));
++#ifdef NIXPKGS_MESA_GL
 +                if (!lib.load()) {
 +                    // Fallback to Mesa driver
-+                    lib.setFileName(QLatin1String("@mesa_lib@/lib/libGL"));
++                    lib.setFileName(QLatin1String(NIXPKGS_MESA_GL));
 +                }
++#endif // NIXPKGS_MESA_GL
                  glXGetProcAddressARB = (qt_glXGetProcAddressARB) lib.resolve("glXGetProcAddressARB");
+ #endif
              }
-         }

pkgs/development/libraries/qt-5/5.8/qtbase/series

@@ -7,3 +7,4 @@ xdg-config-dirs.patch
 compose-search-path.patch
 libressl.patch
 qpa-plugin-path.patch
+dlopen-gl.patch