Modify to handle symplink as well as file

* The current source causes problems when building `sv-parser` on bazel build system
  * because bazel creates the working directory for the build as a symlink

sv-parser-syntaxtree/build.rs

@@ -65,7 +65,7 @@ fn main() {
 
     for entry in WalkDir::new("src") {
         let entry = entry.unwrap();
-        if entry.file_type().is_file() {
+        if entry.path().is_file() {
             let f = File::open(entry.path()).unwrap();
             let f = BufReader::new(f);
             let mut hit_node = false;