The FCM software is required to compile the OSM code, make is not used. Either use the FCM copy bundled with OpenIFS or the Single Column Model. Or, download FCM from the UK Meteorological Office.
Set your environment
Before trying to compile the OSM code, make sure FCM is added to your PATH environment variable so the fcm command can be found.
At ECMWF
The script compile_fcm.ksh is provided that correctly sets the compilation environment by using module load command and then compiling the model code using the command fcm. You may need to edit this script for your own account name and directories.