[recipes] Update README.md for OS X

[Matthias Clasen <matthiasc src gnome org>]

commit 4833461a3c207b9f8981d9c6698e2367892a8192
Author: Riccardo Setti <giskard autistici org>
Date:   Tue Apr 4 10:35:00 2017 +0000

    Update README.md for OS X
    
    Some updates to the brew build instructions.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=780895

 README.md |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)
---
diff --git a/README.md b/README.md
index 54e1ad0..6c14930 100644
--- a/README.md
+++ b/README.md
@@ -52,7 +52,16 @@ brew install automake
 brew install libtool
 brew install gettext
 brew install pkg-config
+brew install mason
 ```
+- MacOS Sierra and Gettext
+On Sierra (at the least) gettext formula is keg only, in order to let the configuration script
+to find msgfmt you will need to link the gettext package into the system. If you think this might
+break other builds I would recommend to unlink (``brew unlink gettext``) after the compilation process.
+```
+brew link --force gettext
+```
+
 - Install GTK+ and other dependencies:
 ```
 brew install gtk+3
@@ -61,7 +70,7 @@ brew install gspell
 ```
 - Clone from git:
 ```
-git clone git://git.gnome.org/recipes
+git clone --recursive git://git.gnome.org/recipes
 ```
 - Build from git as usual, disabling some problematic dependencies:
 ```