compile_ib_files.py: Handle non-zero ibtool return code.

Without check_output() the Popen() will always return None as returncode, this
prevents error handling during the build process.

With check_output() it will raise an exception in case of non-zero return code.

BUG=None

Review-Url: https://codereview.chromium.org/2947393002
Cr-Commit-Position: refs/heads/master@{#481948}

build/config/mac/compile_ib_files.py

@@ -40,17 +40,21 @@ def main():
 
   ibtool_section_re = re.compile(r'/\*.*\*/')
   ibtool_re = re.compile(r'.*note:.*is clipping its content')
-  ibtoolout = subprocess.Popen(ibtool_args, stdout=subprocess.PIPE)
+  try:
+    stdout = subprocess.check_output(ibtool_args)
+  except subprocess.CalledProcessError as e:
+    print(e.output)
+    raise
   current_section_header = None
-  for line in ibtoolout.stdout:
+  for line in stdout.splitlines():
     if ibtool_section_re.match(line):
       current_section_header = line
     elif not ibtool_re.match(line):
       if current_section_header:
-        sys.stdout.write(current_section_header)
+        print(current_section_header)
         current_section_header = None
-      sys.stdout.write(line)
-  return ibtoolout.returncode
+      print(line)
+  return 0
 
 
 if __name__ == '__main__':