Update README.md

docs/README.md

@@ -34,6 +34,15 @@ The main binaries that will be built are:
 - `unittest` is the test runner of duckdb. Again, the extension is already linked into the binary.
 - `<extension_name>.duckdb_extension` is the loadable binary as it would be distributed.
 
+### Tips for speedy builds
+DuckDB extensions will currently rely on DuckDB's build system to provide easy testing and destributing. This does however come at a slightdownside of requiring the template to build DuckDB and its unittester every time you build your extension. To mitigate this, we highly recommend installing [ccache](https://ccache.dev/) and [ninja](https://ninja-build.org/). This will ensure you only need to build core DuckDB once and allows for rapid rebuilds.
+
+To build using ninja and ccache ensure both are installed and run:
+
+```sh
+GEN=ninja make
+```
+
 ## Running the extension
 To run the extension code, simply start the shell with `./build/release/duckdb`. This shell will have the extension pre-loaded.