OSX/CI: oxygen fails to build on branch master

[Marko Käning]

CMake Error at liboxygen/CMakeLists.txt:78 (install):
  install TARGETS given no LIBRARY DESTINATION for shared library target
  "oxygenstyle5".


CMake Error at liboxygen/CMakeLists.txt:148 (install):
  install TARGETS given no LIBRARY DESTINATION for shared library target
  "oxygenstyleconfig5".