don't emit rerun-if-changed unless the path exists and is readable

Author: reaperhulk

openssl-sys/build/main.rs

@@ -83,8 +83,11 @@ fn main() {
     // 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);
+    let potential_path = include_dir.join("openssl");
+    if potential_path.exists() {
+        if let Some(printable_include) = potential_path.to_str() {
+            println!("cargo:rerun-if-changed={}", printable_include);
+        }
     }
 
     if !lib_dirs.iter().all(|p| p.exists()) {