clippy-driver: use rustc_tools_util to get version info.

This will add git hash information to `clippy-driver -V` output.

clippy_lints/src/consts.rs

@@ -344,7 +344,7 @@ impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
                 }
                 ret
             },
-            // FIXME: cover all useable cases.
+            // FIXME: cover all usable cases.
             _ => None,
         }
     }

src/driver.rs

@@ -10,13 +10,11 @@ extern crate rustc_interface;
 extern crate rustc_plugin;
 
 use rustc_interface::interface;
+use rustc_tools_util::*;
+
 use std::path::Path;
 use std::process::{exit, Command};
 
-fn show_version() {
-    println!(env!("CARGO_PKG_VERSION"));
-}
-
 /// If a command-line option matches `find_arg`, then apply the predicate `pred` on its value. If
 /// true, then return it. The parameter is assumed to be either `--arg=value` or `--arg value`.
 fn arg_value<'a>(
@@ -117,7 +115,8 @@ pub fn main() {
             use std::env;
 
             if std::env::args().any(|a| a == "--version" || a == "-V") {
-                show_version();
+                let version_info = rustc_tools_util::get_version_info!();
+                println!("{}", version_info);
                 exit(0);
             }