add Makefile, macOS Ninja preset, optional VST2 SDK

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.

CMakePresets.json

@@ -5,6 +5,32 @@
 		"patch": 0
 	},
 	"version": 5,
+	"configurePresets": [
+		{
+			"condition": {
+				"lhs": "${hostSystemName}",
+				"rhs": "Darwin",
+				"type": "equals"
+			},
+			"displayName": "Build with Ninja on macOS",
+			"generator": "Ninja Multi-Config",
+			"inherits": "base",
+			"name": "macos"
+		}
+	],
+	"buildPresets": [
+		{
+			"condition": {
+				"lhs": "${hostSystemName}",
+				"rhs": "Darwin",
+				"type": "equals"
+			},
+			"configurePreset": "macos",
+			"displayName": "Build with Ninja on macOS",
+			"inherits": "base",
+			"name": "macos"
+		}
+	],
 	"include": [
 		"modules/gin/ci/toolchains/xcode.json",
 		"modules/gin/ci/toolchains/vs.json",