mention about x.py setup in INSTALL.md

Signed-off-by: onur-ozkan <[email protected]>

Author: onur-ozkan

INSTALL.md

@@ -97,6 +97,11 @@ See [the rustc-dev-guide for more info][sysllvm].
    `sysconfdir` values are combined with the path from the `DESTDIR`
    environment variable.
 
+   If you are unsure what to use in build configurations and need a good default one,
+   you will likely find `x.py setup` more user-friendly. It's an interactive command that
+   offers a better experience compared to the `configure` script, and guides you through
+   selecting a config profile, setting up LSP, configuring git hooks, etc.
+
 3. Build and install:
 
    ```sh