File reproducible.patch of Package difftastic

https://github.com/Wilfred/difftastic/pull/813 

Avoid a race in rust
that caused random variations in the binary every time
breaking reproducible builds.

diff --git a/build.rs b/build.rs
index 5c5b4f6..232f6fd 100644
--- a/build.rs
+++ b/build.rs
@@ -264,7 +264,7 @@ fn main() {
         println!("cargo:rerun-if-changed={}", parser.src_dir);
     }
 
-    parsers.par_iter().for_each(|p| p.build());
+    parsers.iter().for_each(|p| p.build());
     commit_info();
 
     if let Some((version, _, _)) = rustc::triple() {