don't emit rerun-if-changed when vendoring

openssl-sys/build/main.rs

@@ -79,6 +79,10 @@ fn main() {
     let target = env::var("TARGET").unwrap();
 
     let (lib_dirs, include_dir) = find_openssl(&target);
+    // rerun-if-changed causes openssl-sys to rebuild if the openssl include
+    // dir has changed since the last build. However, this causes a rebuild
+    // every time when vendoring so we disable it.
+    #[cfg(not(feature = "vendored"))]
     if let Some(printable_include) = include_dir.join("openssl").to_str() {
         println!("cargo:rerun-if-changed={}", printable_include);
     }