Trying to build darktable 2.2.3 in current Cauldron triggers this CMake error:

```
CMake Error at //lib64/cmake/llvm/LLVMExports.cmake:777 (message):
  The imported target "LLVMSupport" references the file

     "/usr/lib64/libLLVMSupport.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

     "//lib64/cmake/llvm/LLVMExports.cmake"

  but not all the files it references.

Call Stack (most recent call first):
  /lib64/cmake/llvm/LLVMConfig.cmake:151 (include)
  CMakeLists.txt:324 (find_package)


-- Configuring incomplete, errors occurred!
```

The issue is that %{_lib}llvm-devel provides `%{_libdir}/cmake/llvm/LLVMExports.cmake`, which apparently requires the static libraries to work properly.

I'm not sure yet what is the proper fix, I had added llvm-static as a dependency of %{_lib}llvm-devel, but it caused some issues (especially with rust which buildconflicts llvm-static - and that was kind of a dirty fix anyway).