Migrated from Make to CMake.

docs/STEINBERG.md

@@ -25,6 +25,12 @@ check without adding a C++ runtime or network dependency to libxtc.
 - The C render example demonstrates the actual xtc plugin facade and WAV writer,
   including no-clobber output, without requiring JACK or a GUI.
 
+Enable the root CMake integration with `-DXTC_BUILD_STEINBERG=ON` and
+`-DXTC_VST3_SDK_ROOT=/path/to/vst3sdk`, build, then run
+`ctest --test-dir build --output-on-failure -R steinberg`. Normal builds leave
+the SDK option off. The example subdirectory also remains a standalone CMake
+entry point for native SDK/ASIO diagnostics.
+
 See [the example instructions](../examples/steinberg/README.md) for SDK versions,
 build commands, validation and ASIO diagnostics.