Create the "tmp" and "bin" directories beforehand if they don't exist already. Then run
cd src/game
-fpc -O3 -Fi../lib/vampimg -Fi../lib/vampimg/JpegLib -Fi../lib/vampimg/ZLib -Fu../lib/vampimg -Fu../lib/vampimg/JpegLib -Fu../lib/vampimg/ZLib -FE../../bin -FU../../tmp Doom2DF.dpr
+fpc -O3 -Fi../lib/vampimg -Fi../lib/vampimg/JpegLib -Fi../lib/vampimg/ZLib -Fu../lib/vampimg -Fu../lib/vampimg/JpegLib -Fu../lib/vampimg/ZLib -FE../../bin -FU../../tmp Doom2DF.lpr
If you want SDL_mixer instead of FMOD, add -dUSE_MIXER.
To build a headless (no video/audio, for dedicated servers) executable, add -dHEADLESS.