Added "/utf-8" to Windows compilation options. (#603)

helix-syntax/build.rs

@@ -77,7 +77,8 @@ fn build_library(src_path: &Path, language: &str) -> Result<()> {
         command
             .args(&["/nologo", "/LD", "/I"])
             .arg(header_path)
-            .arg("/Od");
+            .arg("/Od")
+            .arg("/utf-8");
         if let Some(scanner_path) = scanner_path.as_ref() {
             command.arg(scanner_path);
         }