Bug 495217

Trying to compile Qt 6.7 with kdesrc-build with instructions from https://community.kde.org/Get_Involved/development/More#Build_Qt_using_kdesrc-build results in the following error when trying to compile qttools:

```
CMake Error at /usr/lib/x86_64-linux-gnu/cmake/zstd/zstdTargets.cmake:42 (message): Some (but not all) targets in this export set were already defined.
  Targets Defined: zstd::libzstd_shared, zstd::libzstd_static
  Targets not yet defined: zstd::libzstd

Call Stack (most recent call first):
   /usr/lib/x86_64-linux-gnu/cmake/zstd/zstdConfig.cmake:42 (include)
   /home/redacted/kde/src/qtbase/cmake/FindWrapZSTD.cmake:24 (find_package)
   /home/redacted/kde/src/qtbase/cmake/QtFindPackageHelpers.cmake:141 (find_package)
   src/designer/src/lib/CMakeLists.txt:425 (qt_find_package)
```

- Kubuntu 24.10.
- Trying to compile KDE's Qt from the 6.7 branch
- (from Ubuntu apt sources) libzstd-dev = 1.5.6+dfsg-1
- (from Ubuntu apt sources) clang-19, llvm-19, libclang-19-dev, and related dev packages = 1:19.1.1-1ubuntu1

**WORKAROUND**
Disabling QtDesigner build from the command line seems to work. i.e the following full command line:

```
kdesrc-build qt6-set --cmake-options="-DQT_FEATURE_xcb=ON -DQT_FEATURE_designer=OFF -DQT_FEATURE_assistant=OFF"
```

For some reason (probably lack of knowledge), supplying the `-DQT_FEATURE_designer=OFF` or `-DQT_FEATURE_zstd=OFF` in the file `~/.local/state/sysadmin-repo-metadata/module-definitions/qt6.ksb` did not fix it.

**ADDITIONAL INFORMATION**

There are similar (but not identical) errors regarding the zstd on Qt bug tracker, but they seem to not apply here or have been fixed in version 6.7.3, which is already available during this compilation. Setting `branch 6.8` in qt6.ksb does not seem to have any effect either.