Run the add_compile_options command unit test.

This has not been executed since it was added in
commit a984f325 (Introduce add_compile_options command., 2013-06-04).
cmTarget: Don't update IMPORTED target compilation properties

The include_directories() and add_compile_options() commands
should not append to the corresponding target property for IMPORTED
targets.  This is already the case for add_definitions().
Merge topic 'minor-cleanups' into next

07e5ff9 cmTarget: Don't update IMPORTED target compilation properties
be291ae Run the add_compile_options command unit test.