qt5.qtbase: fix mysql support for cross builds

And fix build with strictDeps enabled

Co-Authored-By: eryngion <eryngion@protonmail.com>

pkgs/development/libraries/qt-5/5.15/default.nix

@@ -49,6 +49,10 @@ let
         url = "https://gitlab.alpinelinux.org/alpine/aports/-/raw/81b14ae4eed038662b53cd20786fd5e0816279ec/community/qt5-qtbase/loongarch64.patch";
         hash = "sha256-BnpejF6/L73kVVts0R0/OMbVN8G4DXVFwBMJPLU9QbE=";
       })
+      (fetchpatch {
+        url = "https://salsa.debian.org/qt-kde-team/qt/qtbase/-/raw/6910758e1141f8ea65a8f2359ac30163d65bf6e2/debian/patches/cross_build_mysql.diff";
+        hash = "sha256-tzmmLmMXmeDwRVjdpWekDJvSkrIIlslC12HP7XPcm3E=";
+      })
     ];
     qtdeclarative = [
       ./qtdeclarative.patch

pkgs/development/libraries/qt-5/modules/qtbase.nix

@@ -65,8 +65,7 @@
   # options
   libGLSupported ? !stdenv.hostPlatform.isDarwin,
   libGL,
-  # qmake detection for libmysqlclient does not seem to work when cross compiling
-  mysqlSupport ? stdenv.hostPlatform == stdenv.buildPlatform,
+  mysqlSupport ? true,
   libmysqlclient,
   buildExamples ? false,
   buildTests ? false,
@@ -534,12 +533,6 @@ stdenv.mkDerivation (
             "-I"
             "${cups.dev}/include"
           ]
-          ++ lib.optionals mysqlSupport [
-            "-L"
-            "${libmysqlclient}/lib"
-            "-I"
-            "${libmysqlclient}/include"
-          ]
           ++ lib.optionals (qttranslations != null) [
             "-translationdir"
             "${qttranslations}/translations"