Accept missing static_files dir

src/build.rs

@@ -1,5 +1,6 @@
 use std::env;
 use std::fs::{read_dir, File};
+use std::io::ErrorKind::NotFound;
 use std::io::Read;
 use std::io::Write;
 use std::path::{Path, PathBuf};
@@ -20,7 +21,9 @@ pub fn create_static_output_files(source_dir: &str) {
   let out_dir = env::var("OUT_DIR").unwrap();
   let dest_path = Path::new(&out_dir).join("static_files.rs");
   let mut f = File::create(&dest_path).unwrap();
-  for maybe_dir_entry in read_dir(source_dir).unwrap() {
+  match read_dir(source_dir) {
+    Ok(dir_content) => {
+      for maybe_dir_entry in dir_content {
         let file_path = maybe_dir_entry.unwrap().path();
         let mut buffer = String::new();
         File::open(file_path.clone())
@@ -40,6 +43,14 @@ pub fn create_static_output_files(source_dir: &str) {
         .unwrap();
       }
     }
+    Err(err) => {
+      if err.kind() == NotFound {
+      } else {
+        Err(err).unwrap()
+      }
+    }
+  }
+}
 
 #[allow(unused)]
 fn main() {