Drop debug output code that writes to source dir

cargo publish isn't happy with build.rs modifying source dir, and this piece of
code doesn't seem to do anything other than writing the compiler options used
to disk.

sys/build.rs

@@ -5,7 +5,7 @@ extern crate pkg_config;
 extern crate regex;
 
 use std::env;
-use std::fs::{self, create_dir, symlink_metadata, File};
+use std::fs::{self, File};
 use std::io::{self, BufRead, BufReader, Write};
 use std::path::{Path, PathBuf};
 use std::process::Command;
@@ -978,19 +978,6 @@ fn main() {
         ],
     );
 
-    let tmp = output().join("tmp");
-    if symlink_metadata(&tmp).is_err() {
-        create_dir(&tmp).expect("Failed to create temporary output dir");
-    }
-    let mut f = File::create(tmp.join(".build")).expect("Filed to create .build");
-    let tool = cc::Build::new().get_compiler();
-    write!(f, "{}", tool.path().to_string_lossy().into_owned()).expect("failed to write cmd");
-    for arg in tool.args() {
-        write!(f, " {}", arg.to_str().unwrap()).expect("failed to write arg");
-    }
-    for dir in &include_paths {
-        write!(f, " -I {}", dir.to_string_lossy().into_owned()).expect("failed to write incdir");
-    }
     let clang_includes = include_paths
         .iter()
         .map(|include| format!("-I{}", include.to_string_lossy()));