Replaces the git FetchContent and the global BUILD_TESTS cache override; same vendored/URL/offline resolution as libchdr. OFF stays network-free. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Adapted from the original feature commits, retaining their author credit: [22bdc9e9](https://github.com/FractalEngineer/psxrecomp/commit/22bdc9e90d14f7a04b79c83b77611c4eb980fef4) [5a1264b7](https://github.com/FractalEngineer/psxrecomp/commit/5a1264b79b69b5d75f7b8507e305b1e13a911a50) [ac6f84ba](https://github.com/FractalEngineer/psxrecomp/commit/ac6f84ba039b1d27bb1e93d3b6d05390dfa42ff9) [734977c9](https://github.com/FractalEngineer/psxrecomp/commit/734977c93e80789e9210a262daa35a88f41c40d4) [04714837](https://github.com/FractalEngineer/psxrecomp/commit/04714837245ebe68abbc462ac6822a3818eedf67) [5bafeebf](https://github.com/FractalEngineer/psxrecomp/commit/5bafeebf3f0c2eaaa38212f960b9f6f88351cb74) Source scope and current-master validation: docs/internal/upstream/experimental-openxr-win32-gl.md Co-authored-by: Yves <calibratedbeats@gmail.com>