Use a new-style Cargo build script.

Cargo.toml

@@ -4,7 +4,7 @@ name = "js"
 version = "0.1.0"
 authors = ["The Servo Project Developers"]
 
-build = "make -f makefile.cargo"
+build = "build.rs"
 
 [features]
 debugmozjs = ['mozjs-sys/debugmozjs']

build.rs

@@ -0,0 +1,18 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#![feature(io)]
+
+use std::old_io::process::{Command, ProcessExit, StdioContainer};
+
+
+fn main() {
+    let result = Command::new("make")
+        .args(&["-f", "makefile.cargo"])
+        .stdout(StdioContainer::InheritFd(1))
+        .stderr(StdioContainer::InheritFd(2))
+        .status()
+        .unwrap();
+    assert_eq!(result, ProcessExit::ExitStatus(0));
+}

makefile.cargo

@@ -20,7 +20,7 @@ ifneq (,$(CARGO_FEATURE_DEBUGMOZJS))
 	CFLAGS += -g -O0 -DDEBUG -D_DEBUG
 endif
 
-MOZJS_OUTDIR = $(shell find $(OUT_DIR)/.. -name 'mozjs-sys-*' -type d)
+MOZJS_OUTDIR = $(shell find $(OUT_DIR)/../.. -name 'mozjs-sys-*' -type d)/out
 CFLAGS += -I$(MOZJS_OUTDIR)/dist/include
 
 .PHONY: all