- Add --keep-cache option to control whether or not to retain the
External/build/Intermediates directory (default not retained).
- Export KEEP_CACHE & SKIP_PACKAGING to be available within scripts
used by ExternalDependencies Xcode builds.
- Move BLD_SPECIFIED to build() instead of build_impl() to avoid
updating it from background thread (which will fail).
- Update MoltenVK version to 1.2.7 (unrelated).
- Add CompilerMSL::Options::replace_recursive_inputs to pipeline cache (unrelated).
- Update GitHub CI to Xcode 15.0.
- Update Whats_new.md document.
Log ext lib build steps to provide user feedback.
Add package_ext_libs_finish.sh script to separate packaging
libraries from building them, to avoid build database conflicts.
Travis only build macOS ext libs.
