cmake: use pkg-config + test compile instead of Find module for detecting rpi

[madebr]

• Blind rpi fix
• Fixes SDL_HIDAPI_LIBUSB

Fixes #8050

@slouken
Can you please test this?
I don't have a rpi configured right now, so I can't test it.

[slouken]

-- Performing Test HAVE_RPI - Success
CMake Error at cmake/sdltargets.cmake:59 (get_property):
  get_property not given name for TARGET scope.
Call Stack (most recent call first):
  cmake/sdlchecks.cmake:1111 (sdl_generic_link_dependency)
  CMakeLists.txt:1439 (CheckRPI)

[slouken]

Much closer:

/usr/bin/ld: cannot find -lbcm_host

[slouken]

Where this is found varies by distribution, but here it's in /opt/vc/lib/libbcm_host.so

[slouken]

Adding -l/opt/vc/lib to the link line works here.

[madebr]

Does pkg-config bcm_host or pkg-config brcmegl work?
I'm wondering whether /opt/vc/lib/pkgconfig is in the default PKG_CONFIG_PATH.

[slouken]

It appears not to be:

$ ls /opt/vc/lib/pkgconfig
bcm_host.pc  brcmegl.pc  brcmglesv2.pc  brcmvg.pc  mmal.pc  vcsm.pc
$ pkg-config bcm_host --libs
Package bcm_host was not found in the pkg-config search path.
Perhaps you should add the directory containing `bcm_host.pc'
to the PKG_CONFIG_PATH environment variable
No package 'bcm_host' found

[slouken]

$ PKG_CONFIG_PATH=/opt/vc/lib/pkgconfig pkg-config bcm_host --libs
-L/opt/vc/lib -lbcm_host -lvcos -lvchiq_arm -pthread
$ PKG_CONFIG_PATH=/opt/vc/lib/pkgconfig pkg-config brcmegl --libs
-L/opt/vc/lib -lbrcmEGL -lbrcmGLESv2 -lbcm_host -lvchostif -lbcm_host -lvcos -lvchiq_arm -pthread

[madebr]

Can you try again? It now sets the PKG_CONFIG_PATH environment variable.

[slouken]

Looks good, thanks! Should I merge, or are you still iterating?

[madebr]

Looks good, thanks! Should I merge, or are you still iterating?

I think the check_c_source_compiles can be removed.

I also think SDL does not need to link to brcmegl if it turned out bcm_host.pc and brcmegl.pc were never actually used before.

Can you re-build SDL in a clean build folder?

[slouken]

It works great!

[madebr]

Merging.
For completeness, this pr also renames SDL_TEST -> SDL_TEST_LIBRARY.
See 41a96c8#commitcomment-122911331