Fix copy'n'paste mistake in build.rs.

Change-Id: Iccd91302a1729023ce88b9c94888b7eba8fa6330
diff --git a/build.rs b/build.rs
index 3bd87c0..7b5130d 100644
--- a/build.rs
+++ b/build.rs
@@ -3,7 +3,7 @@
 
 fn main() {
     // Generate C header bindings.
-    println!("cargo:rerun-if-changed=wrapper.h");
+    println!("cargo:rerun-if-changed=bindings.h");
 
     let bindings = bindgen::Builder::default()
         .header("bindings.h")