$ make
[ 59%] Built target chipmunk_static
Linking C executable falling_time
CMakeFiles/falling_time.dir/high_score.c.o: In function `HighScoresInit':
high_score.c:(.text+0x2f): undefined reference to `get_user_config_file'
CMakeFiles/falling_time.dir/high_score.c.o: In function `HighScoresAdd':
high_score.c:(.text+0x23d): undefined reference to `get_user_config_file'
collect2: error: ld returned 1 exit status
CMakeFiles/falling_time.dir/build.make:565: recipe for target 'falling_time' failed
make[2]: *** [falling_time] Error 1
CMakeFiles/Makefile2:60: recipe for target 'CMakeFiles/falling_time.dir/all' failed
make[1]: *** [CMakeFiles/falling_time.dir/all] Error 2
Makefile:137: recipe for target 'all' failed
make: *** [all] Error 2