littlecat@littlecat-HP-15-Notebook-PC:~/SRB2$ make -C src/ LINUX64=1
make: Entering directory `/home/littlecat/SRB2/src'
sdl/i_system.c: In function ‘I_StartupKeyboard’:
sdl/i_system.c:749:9: error: ‘SIGBREAK’ undeclared (first use in this function)
  signal(SIGBREAK , quit_handler);
         ^
sdl/i_system.c:749:9: note: each undeclared identifier is reported only once for each function it appears in
sdl/i_system.c: In function ‘I_Error’:
sdl/i_system.c:2370:13: error: ‘buffer’ undeclared (first use in this function)
    vsprintf(buffer, error, argptr);
             ^
make: *** [../objs/Linux64/SDL/Release/i_system.o] Error 1
make: Leaving directory `/home/littlecat/SRB2/src'