modules/ is gitignored, so local Gin edits cannot live in the submodule.
They are stored in patches/ and re-applied (idempotently) before every
configure and build via 'make apply-patches'.
Also improve the submodule guard: git submodule update is a no-op here,
so print concrete restore instructions instead.
CMakePresets.json includes the gin toolchain presets, so configuring
fails with a bare "File not found" when the submodules are missing or a
git submodule update is in flight. Report the missing path and the fix
instead.
Build with a plain "make install": it builds via CMake presets, installs
the AU/VST3/CLAP bundles into ~/Library/Audio/Plug-Ins and syncs the
factory presets and wavetables to /Library/Audio/Presets, which is the
only location the plugin reads them from on macOS.
Adds a macOS Ninja Multi-Config preset for faster incremental builds, and
drops the VST format when the non-redistributable plugin_sdk submodule is
not checked out so the remaining formats still build.
