Building 3.9.1 and finding SDL2 built with autotools

[Barry Jackson]

gnuradio & cmake seem not to be able to detect the presence of sdl2 
development files.

 -- Configuring gr-video-sdl support...
--   Dependency SDL_FOUND = FALSE
--   Dependency Boost_FOUND = TRUE
--   Dependency ENABLE_GNURADIO_RUNTIME = ON
--   Disabling gr-video-sdl support.
--   Override with -DENABLE_GR_VIDEO_SDL=ON/OFF

I can see nothing in the CMakeList.txt to enable it to find sdl2.pc and 
use it, however my cmake knowledge is small.

Obviously there are no cmake files packaged with sdl2 as the package is 
not build using cmake.

In earlier versions we had no issues building with sdl support so has 
something changed?

Any help would be appreciated.

Barry
(GR maintainer for Mageia)