message: Add note for the patch to GYP.
diff: @@ -52,6 +52,15 @@ make
  ## Build with GYP (stable)
  +### Apply a patch to GYP
  +
  +The upstream GYP may or may not work on macOS for Mozc.
  +You probably need to apply the following patch to GYP.
  +
  +```
  +cd src\third_party\gyp
  +git apply ..\..\gyp\gyp.patch
  +```
  ### Build main converter and composition UI.
  