Setting swift compiler flags per file

Hi!


I'm trying to make the swift compiler optimize only a single file (in Debug configuration I would like to have optimization off, except this single file).


I went to the Build Phases, and added "-O" to the Compiler Flags to that file, but it doesn't seem to have any effect. In the debug logs I can see the command to compile that file, and "-Onone" is among the arguments there, but there is no "-O".


What am I doing wrong? Is it possible at all to set separate optimization level for a single file?


Thanks,

Zsombor