Add a dependency for the VST3 SDK

meson_options.txt

@@ -12,6 +12,13 @@ option(
   description : 'Enable static linking for Boost. Needed when distributing the binaries to other systems.'
 )
 
+option(
+  'with-vst3',
+  type : 'boolean',
+  value : true,
+  description : 'Whether to build the VST3 version of yabridge. This requires CMake to be installed.'
+)
+
 option(
   'with-winedbg',
   type : 'boolean',