rebuild if build.rs changed

Author: umanwizard

build.rs

@@ -1,5 +1,6 @@
 fn main() {
     println!("cargo:rerun-if-changed=src/customlabels.cpp");
+    println!("cargo:rerun-if-changed=./build.rs");
     println!("cargo:rerun-if-changed=src/customlabels.h");
     println!("cargo:rerun-if-changed=./dlist");