fix build error on windows (#741)

build.rs

@@ -1,7 +1,13 @@
 use std::{
-	os::unix::process::ExitStatusExt,
 	process::{Command, ExitStatus, Output},
 };
+
+#[cfg(not(target_os = "windows"))]
+use std::os::unix::process::ExitStatusExt;
+
+#[cfg(target_os = "windows")]
+use std::os::windows::process::ExitStatusExt;
+
 fn main() {
 	let output = String::from_utf8(
 		Command::new("git")