[Linux] CMake fails to search for system libtinygltf to link against when USE_SYSTEM_LIBS=ON is declared #399
Description
Despite this core having one of the more-polished buildsystems in the entire libretro pantheon, the dependency on libtinygltf seems to have been "left out in the cold" when compared to the others. If possible it would be great to bring the evaluation of this dependency into parity with the rest, especially since it's so ubiquitously available in the various distribution package archives (Debian since v10 "Buster" and Ubuntu since 20.10 "Groovy Gorilla"; ~six years ago for both, including two LTS releases for the latter). This functionality would permit a size reduction to both the source and binary packages built for this core by obviating the need to clone the needed Git submodule and compile the subsequent artifacts to add to the core.