Merge pull request #1213 from Zokrates/fix-build-script

Fix zokrates_js build script, filter .zok files

zokrates_js/build.rs

@@ -14,7 +14,9 @@ fn export_stdlib() {
     for entry in WalkDir::new(root)
         .into_iter()
         .map(Result::unwrap)
-        .filter(|e| !e.file_type().is_dir())
+        .filter(|e| {
+            !e.file_type().is_dir() && e.path().extension().map(|e| e == "zok").unwrap_or(false)
+        })
     {
         let path: &Path = entry.path();
         let source = fs::read_to_string(path).unwrap();