Windows long is always 4 bytes wide

Author: filmor

Diff for: rustler_sys/build.rs

@@ -27,12 +27,13 @@ fn try_gen_api(dst: &Path, pointer_size: usize) -> bool {
 }
 
 fn main() {
-    // get size of C pointer
-    let target_pointer_width = match env::var("CARGO_CFG_TARGET_POINTER_WIDTH") {
-        Ok(ref val) if val == "32" => 4,
-        Ok(ref val) if val == "64" => 8,
-        Ok(ref val) => panic!("Unsupported target pointer width: {}", val),
-        Err(err) => panic!(
+    // get size of C long
+    let long_width = match (env::var("CARGO_CFG_TARGET_POINTER_WIDTH"), env::var("CARGO_CFG_TARGET_OS")) {
+        (_, Ok(ref os)) if os == "windows" => 4,
+        (Ok(ref val), _) if val == "32" => 4,
+        (Ok(ref val), _) if val == "64" => 8,
+        (Ok(ref val), _) => panic!("Unsupported target pointer width: {}", val),
+        (Err(err), _) => panic!(
             "An error occurred while determining the pointer width to compile `rustler_sys` for:\n\n{:?}\n\nPlease report a bug.",
             err
         ),