Include printing of "cargo:rerun-if-changed" in tutorial

Author: dennisschagt

book/src/tutorial.md

@@ -204,6 +204,10 @@ fn main() {
     cxx_build::bridge("src/main.rs")
         .file("src/blobstore.cc")
         .compile("cxx-demo");
+
+    println!("cargo:rerun-if-changed=src/main.rs");
+    println!("cargo:rerun-if-changed=src/blobstore.cc");
+    println!("cargo:rerun-if-changed=include/blobstore.h");
 }
 ```