Cannot use Clang. CMake cannot find "clangBasic"

Hello,

I am trying to build CastXML dependency.

CastXML is looking for Clang. But it cannot find it.

========================================================================
Building module castxml in /home/kev/Desktop/Software/org.tomviz.Tomviz/.flatpak-builder/build/castxml-9
========================================================================
-- The C compiler identification is GNU 10.2.0
-- The CXX compiler identification is GNU 10.2.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Error at /usr/lib/x86_64-linux-gnu/cmake/clang/ClangTargets.cmake:356 (message):
  The imported target "clangBasic" references the file

     "/usr/lib/x86_64-linux-gnu/libclangBasic.a"

  but this file does not exist.  Possible reasons include:

  * The file was deleted, renamed, or moved to another location.

  * An install or uninstall procedure did not complete successfully.

  * The installation package was faulty and contained

     "/usr/lib/x86_64-linux-gnu/cmake/clang/ClangTargets.cmake"

  but not all the files it references.

Call Stack (most recent call first):
  /usr/lib/x86_64-linux-gnu/cmake/clang/ClangConfig.cmake:19 (include)
  CMakeLists.txt:75 (find_package)

 /usr/lib/x86_64-linux-gnu/cmake/clang/ClangConfig.cmake:19 (include)  CMakeLists.txt:75 (find_package)
-- Configuring incomplete, errors occurred!

I tried include freedesktop and KDE Sdk ,setting the env variable, but no luck.
I add org.freedesktop.Sdk.Extension.llvm11 which does not work.
I’m not sure what I’m missing. I search flathub github, but no one use CastXML at the moment.

Thanks.