Fix calling js2c

tools/coffee2c.py

@@ -1,15 +1,16 @@
 #!/usr/bin/env python
 
+import contextlib
 import os
 import subprocess
 import sys
 
 
-SOURCE_ROOT = os.path.dirname(os.path.dirname(__file__))
+SOURCE_ROOT = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))
 
 
 def main():
-  natives = sys.argv[1]
+  natives = os.path.abspath(sys.argv[1])
   coffee_source_files = sys.argv[2:]
 
   output_dir = os.path.dirname(natives)
@@ -35,7 +36,21 @@ def call_compile_coffee(source_file, output_filename):
 
 def call_js2c(natives, js_source_files):
   js2c = os.path.join(SOURCE_ROOT, 'vendor', 'node', 'tools', 'js2c.py')
-  subprocess.check_call([sys.executable, js2c, natives] + js_source_files)
+  src_dir = os.path.dirname(js_source_files[0])
+  with scoped_cwd(src_dir):
+    subprocess.check_call(
+        [sys.executable, js2c, natives] +
+        [os.path.basename(source) for source in js_source_files])
+
+
+@contextlib.contextmanager
+def scoped_cwd(path):
+  cwd = os.getcwd()
+  os.chdir(path)
+  try:
+    yield
+  finally:
+    os.chdir(cwd)
 
 
 if __name__ == '__main__':