diff --git a/sys/build.rs b/sys/build.rs
index 0015ec4..52f84f5 100644
--- a/sys/build.rs
+++ b/sys/build.rs
@@ -3,7 +3,7 @@ extern crate gcc;
 extern crate pkg_config;
 
 use std::env;
-use std::fs::{self, File};
+use std::fs::{self, create_dir, File, symlink_metadata};
 use std::io::{self, Write, BufRead, BufReader};
 use std::path::PathBuf;
 use std::process::Command;
@@ -382,7 +382,7 @@ fn main() {
 		}
 	}
 
-	check_features(include_paths, &vec![
+	check_features(include_paths.clone(), &vec![
 		("libavutil/avutil.h", None, "FF_API_OLD_AVOPTIONS"),
 
 		("libavutil/avutil.h", None, "FF_API_PIX_FMT"),
@@ -487,4 +487,21 @@ fn main() {
 		("libswscale/swscale.h", Some("swscale"), "FF_API_SWS_CPU_CAPS"),
 		("libswscale/swscale.h", Some("swscale"), "FF_API_ARCH_BFIN"),
 	]);
+
+	let tmp = std::env::current_dir().unwrap().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 = gcc::Config::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");
+	}
 }
diff --git a/sys/tests/lib.rs b/sys/tests/lib.rs
index f622d44..b63a1c4 100644
--- a/sys/tests/lib.rs
+++ b/sys/tests/lib.rs
@@ -1,105 +1,103 @@
-extern crate libc;
-extern crate ffmpeg_sys;
-
-use std::env;
-use std::fs::{create_dir, File, symlink_metadata};
-use std::io::Write;
-use std::mem;
-use std::path::{Path, PathBuf};
-use std::process::Command;
-use std::str;
-
-use libc::c_void;
-
-use ffmpeg_sys::AVCodecContext;
-
-fn output() -> PathBuf {
-	let mut ret = std::env::current_dir().unwrap();
-	ret.push(&Path::new("tmp"));
-	if symlink_metadata(&ret).is_err() {
-		create_dir(&ret).expect("Failed to create temporary output dir");
-	}
-	ret
-}
-
-// Checks if byte offsets in C vs. Rust match
-#[test]
-fn check_struct_byte_offsets() {
-	let out_dir = output();
-	let executable = out_dir.join(if cfg!(windows) { "ffmpeg-structs.exe" } else { "ffmpeg-structs" });
-	let compiler =
-		if cfg!(windows) || env::var("MSYSTEM").unwrap_or("".to_string()).starts_with("MINGW32") {
-			"gcc"
-		}
-		else {
-			"cc"
-		};
-
-	println!("Compiling ffmpeg-structs.c");
-
-	if !Command::new(compiler)
-		.arg("-o").arg(&executable)
-		.arg("tests/data/ffmpeg-structs.c")
-		.status()
-		.expect("ffmpeg-structs compile failed")
-		.success() {
-		panic!("ffmpeg-structs compile failed");
-	}
-
-	println!("Running ffmpeg-structs ({:?})", executable);
-	let stdout_raw = Command::new(&executable).current_dir(&out_dir).output().expect("ffmpeg-structs failed").stdout;
-
-	println!("Writing ffmpeg-structs output file");
-	File::create(out_dir.join("ffmpeg-structs.out")).expect("ffmpeg-structs.out 1").write_all(&stdout_raw[..]).expect("ffmpeg-structs.out 2");
-
-	let stdout = str::from_utf8(stdout_raw.as_slice()).unwrap();
-	let mut matching = vec!();
-	let mut errors = vec!();
-
-	// This should check same fields as ffmpeg-structs.c
-	macro_rules! p {
-		($the_struct:ident, $the_field:ident) => {{
-			println!("Test field size for {}::{}", stringify!($the_struct), stringify!($the_field));
-			let ptr : &$the_struct = unsafe { mem::uninitialized() };
-			let expected = format!("[{}::{} @ {}-{}]", stringify!($the_struct), stringify!($the_field), (&ptr.$the_field) as *const _ as usize - ptr as *const _ as usize, mem::size_of_val(&ptr.$the_field));
-
-			if stdout.find(&expected).is_none() {
-				let actual_prefix = format!("[{}::{} @ ", stringify!($the_struct), stringify!($the_field));
-				let mut actual = String::from("not found");
-				for line in stdout.lines() {
-					if line.find(&actual_prefix).is_some() {
-						actual = line.to_string();
-						break
-					}
-				}
-				errors.push(format!("Struct field position as specified in Rust code ({}) is different from C ({})", expected, actual));
-			}
-			else {
-				matching.push(format!("  - {}", expected));
-			}
-		}};
-	}
-
-	p!(AVCodecContext, av_class);
-	p!(AVCodecContext, codec_id);
-	p!(AVCodecContext, bit_rate);
-	p!(AVCodecContext, bit_rate_tolerance);
-	p!(AVCodecContext, width);
-	p!(AVCodecContext, height);
-	p!(AVCodecContext, coded_width);
-	p!(AVCodecContext, pix_fmt);
-	p!(AVCodecContext, sample_rate);
-	p!(AVCodecContext, channels);
-	p!(AVCodecContext, sample_fmt);
-	p!(AVCodecContext, frame_size);
-	p!(AVCodecContext, frame_number);
-	p!(AVCodecContext, block_align);
-
-	// p!(AVCodecContext, b_frame_strategy); // TODO: make conditional somehow with cfg!(feature="ff_api_private_opt")
-
-	println!("These struct fields have matching position/size in Rust and C code:\n{}", matching.join("\n"));
-
-	if !errors.is_empty() {
-		panic!(errors.join("\n"));
-	}
-}
+extern crate libc;
+extern crate ffmpeg_sys;
+
+use std::fs::{create_dir, File, symlink_metadata};
+use std::io::{Write, BufRead, BufReader};
+use std::mem;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+use std::str;
+
+use ffmpeg_sys::AVCodecContext;
+
+fn output() -> PathBuf {
+	let mut ret = std::env::current_dir().unwrap();
+	ret.push(&Path::new("tmp"));
+	if symlink_metadata(&ret).is_err() {
+		create_dir(&ret).expect("Failed to create temporary output dir");
+	}
+	ret
+}
+
+// Checks if byte offsets in C vs. Rust match
+#[test]
+fn check_struct_byte_offsets() {
+	let out_dir = output();
+	let executable = out_dir.join(if cfg!(windows) { "ffmpeg-structs.exe" } else { "ffmpeg-structs" });
+
+    let curr_dir = std::env::current_dir().unwrap();
+	let f = File::open(curr_dir.join("tmp/.build"))
+		.expect("Filed to open .build");
+	let f = BufReader::new(f);
+	let args: Vec<String> = f.lines().nth(0).unwrap().unwrap()
+		.split(' ').map(String::from).collect();
+
+	println!("Compiling ffmpeg-structs.c");
+
+	if !Command::new(&args[0])
+		.args(&args[1..])
+		.arg("-o").arg(&executable)
+		.arg("tests/data/ffmpeg-structs.c")
+		.status()
+		.expect("ffmpeg-structs compile failed")
+		.success() {
+		panic!("ffmpeg-structs compile failed");
+	}
+
+	println!("Running ffmpeg-structs ({:?})", executable);
+	let stdout_raw = Command::new(&executable).current_dir(&out_dir).output().expect("ffmpeg-structs failed").stdout;
+
+	println!("Writing ffmpeg-structs output file");
+	File::create(out_dir.join("ffmpeg-structs.out")).expect("ffmpeg-structs.out 1").write_all(&stdout_raw[..]).expect("ffmpeg-structs.out 2");
+
+	let stdout = str::from_utf8(stdout_raw.as_slice()).unwrap();
+	let mut matching = vec!();
+	let mut errors = vec!();
+
+	// This should check same fields as ffmpeg-structs.c
+	macro_rules! p {
+		($the_struct:ident, $the_field:ident) => {{
+			println!("Test field size for {}::{}", stringify!($the_struct), stringify!($the_field));
+			let ptr : &$the_struct = unsafe { mem::uninitialized() };
+			let expected = format!("[{}::{} @ {}-{}]", stringify!($the_struct), stringify!($the_field), (&ptr.$the_field) as *const _ as usize - ptr as *const _ as usize, mem::size_of_val(&ptr.$the_field));
+
+			if stdout.find(&expected).is_none() {
+				let actual_prefix = format!("[{}::{} @ ", stringify!($the_struct), stringify!($the_field));
+				let mut actual = String::from("not found");
+				for line in stdout.lines() {
+					if line.find(&actual_prefix).is_some() {
+						actual = line.to_string();
+						break
+					}
+				}
+				errors.push(format!("Struct field position as specified in Rust code ({}) is different from C ({})", expected, actual));
+			}
+			else {
+				matching.push(format!("  - {}", expected));
+			}
+		}};
+	}
+
+	p!(AVCodecContext, av_class);
+	p!(AVCodecContext, codec_id);
+	p!(AVCodecContext, bit_rate);
+	p!(AVCodecContext, bit_rate_tolerance);
+	p!(AVCodecContext, width);
+	p!(AVCodecContext, height);
+	p!(AVCodecContext, coded_width);
+	p!(AVCodecContext, pix_fmt);
+	p!(AVCodecContext, sample_rate);
+	p!(AVCodecContext, channels);
+	p!(AVCodecContext, sample_fmt);
+	p!(AVCodecContext, frame_size);
+	p!(AVCodecContext, frame_number);
+	p!(AVCodecContext, block_align);
+
+	// p!(AVCodecContext, b_frame_strategy); // TODO: make conditional somehow with cfg!(feature="ff_api_private_opt")
+
+	println!("These struct fields have matching position/size in Rust and C code:\n{}", matching.join("\n"));
+
+	if !errors.is_empty() {
+		panic!(errors.join("\n"));
+	}
+}