SDL_REVISION doesn't have SDL- prefix when built from an official release tarball

[smcv]

When we take the SDL revision from REVISION.txt, since #14114 was fixed, we add a SDL- prefix.

But if I download SDL3-3.2.28.tar.gz and unpack it, the SDL_revision.h included in the tarball doesn't have that, and neither does its CMake template:

SDL3-3.2.28$ grep SDL_REVISION include/build_config/SDL_revision.h.cmake
#define SDL_REVISION "release-3.2.28-0-g7f3ae3d57 (" SDL_VENDOR_INFO ")"
#define SDL_REVISION "release-3.2.28-0-g7f3ae3d57"
SDL3-3.2.28$ grep SDL_REVISION include/SDL3/SDL_revision.h 
#define SDL_REVISION "Some arbitrary string decided at SDL build time"
#define SDL_REVISION "release-3.2.28-0-g7f3ae3d57 (" SDL_VENDOR_INFO ")"
#define SDL_REVISION "release-3.2.28-0-g7f3ae3d57"

The result is that builds from git can be inspected for their version number with strings | grep SDL-, but builds from official tarballs (which many distros prefer because they can verify the GPG signature) cannot.

[smcv]

For now, I'm going to patch 3.2.28 in Debian (and eventually the Steam Runtime) so it does have this prefix in both of those files.

[slouken]

Fixed in #14577.