framework: expose devel/llvm16 in USES=llvm after b6755d59

$ sed -i '' 's/min=14/min=16/' emulators/yuzu/Makefile
$ make clean all -C emulators/yuzu
[...]
CMake Error at /usr/local/share/cmake/Modules/CMakeDetermineCCompiler.cmake:49 (message):
  Could not find compiler set in environment variable CC:

  clang16.
Call Stack (most recent call first):
  CMakeLists.txt