Add return code to parse_sv

sv-parser/examples/parse_sv.rs

@@ -1,5 +1,6 @@
 use std::collections::HashMap;
 use std::path::PathBuf;
+use std::process;
 use structopt::StructOpt;
 use sv_parser::parse_sv;
 
@@ -23,6 +24,7 @@ struct Opt {
 fn main() {
     let opt = Opt::from_args();
     let mut defines = HashMap::new();
+    let mut exit = 0;
     for path in &opt.files {
         match parse_sv(&path, &defines, &opt.includes) {
             Ok((syntax_tree, new_defines)) => {
@@ -36,7 +38,9 @@ fn main() {
             }
             Err(x) => {
                 println!("parse failed: {:?} ({})", path, x);
+                exit = 1;
             }
         }
     }
+    process::exit(exit);
 }