Yes, I export PFLAGS in this way; the log file says that rtsc.pas is compiled with -mthumb-interwork flag.
Looking at your previous message I see:
arm-elf-gpc -mthumb --gpc-main=main --specs=gba.specs -o prova.o prova.pp /home/gba/bin/../lib/gcc-lib/arm-elf/3.3.1/../../../../arm-elf/bin/ld: /home/gba /bin/../lib/gcc-lib/arm-elf/3.3.1/libgpc.a(init.o)(_p_DoInitProc): warning: inte rworking not enabled.
That error should now vanish (assuming that `init.pas' also is compiled with `-mthumb-interwork' and that `-mthumb-interwork' is the correct flag to enable interworking (you may browse the build log to see what flags `libgcc' is using)). There is one C file in the runtime library (`rts.c'), does it it also use `-mthumb-interwork' flag? If not not this file may be the only remaining problem.