CMake - ffmpeg compilation

[geefr]

Don't have time to fix/test in 5.1, but there's some issues with the ffmpeg cmake stuff. (Can remind me in a month or two if not fixed)

SetupFfmpeg.cmake line 60

list(APPEND SM_FFMPEG_MAKE $(MAKE))
if(WITH_FFMPEG_JOBS GREATER 0)
  list(APPEND SM_FFMPEG_MAKE "-j${WITH_FFMPEG_JOBS}")
endif()

This sets the make command to $(MAKE)

The option WITH_FFMPEG_JOBS is defied as a boolean at the moment (SMDefs.cmake?). Defaults to 'ON' rather than a number.

I think combined, or if you set jobs to an actual number you get $(MAKE);-j4 - cmake will say it built ffmpeg, but the command will silently fail in a subshell somewhere.

Should be:

• Fix WITH_FFMPEG_JOBS option
• use set(SM_FFMPEG_MAKE ${CMAKE_MAKE_PROGRAM}) (Not curly braces)