Improve the Compiling for macOS documentation

- Mention Homebrew to install dependencies easily.
- Remove the part about building fat binaries as support for 32-bit
  macOS was removed in Godot 3.1.
- Improve OSXCross installation instructions.
  - Mention the WSL as an alternative on Windows instead of Cygwin.
  - Change the suggested OSXCross path to something that will work
    out of the box.

development/compiling/compiling_for_osx.rst

@@ -10,10 +10,19 @@ Requirements
 
 For compiling under macOS, the following is required:
 
--  Python 2.7+ or Python 3.5+
--  SCons build system
--  Xcode (or the more lightweight Command Line Tools for Xcode)
--  *Optional* - yasm (for WebM SIMD optimizations)
+- Python 3.5+ (recommended) or Python 2.7+.
+- `SCons <https://www.scons.org>`_ build system.
+- `Xcode <https://apps.apple.com/us/app/xcode/id497799835>`_
+  (or the more lightweight Command Line Tools for Xcode).
+- *Optional* - `yasm <https://yasm.tortall.net/>`_ (for WebM SIMD optimizations).
+
+.. note:: If you have `Homebrew <https://brew.sh/>`_ installed, you can easily
+          install SCons and yasm using the following command::
+
+              brew install scons yasm
+
+          Installing Homebrew will also fetch the Command Line Tools
+          for Xcode automatically if you don't have them already.
 
 .. seealso:: For a general overview of SCons usage for Godot, see
              :ref:`doc_introduction_to_the_buildsystem`.
@@ -21,55 +30,37 @@ For compiling under macOS, the following is required:
 Compiling
 ---------
 
-Start a terminal, go to the root dir of the engine source code and type:
-
-::
+Start a terminal, go to the root directory of the engine source code and type::
 
     scons platform=osx --jobs=$(sysctl -n hw.logicalcpu)
 
 If all goes well, the resulting binary executable will be placed in the
-"bin" subdirectory. This executable file contains the whole engine and
+``bin/`` subdirectory. This executable file contains the whole engine and
 runs without any dependencies. Executing it will bring up the project
 manager.
 
 To create an .app like in the official builds, you need to use the template
-located in ``misc/dist/osx_tools.app``. Typically, for a ".64" optimised binary
-built with `scons p=osx target=release_debug`:
-
-::
+located in ``misc/dist/osx_tools.app``. Typically, for an optimized editor
+binary built with ``scons p=osx target=release_debug``::
 
     user@host:~/godot$ cp -r misc/dist/osx_tools.app ./Godot.app
     user@host:~/godot$ mkdir -p Godot.app/Contents/MacOS
     user@host:~/godot$ cp bin/godot.osx.tools.64 Godot.app/Contents/MacOS/Godot
     user@host:~/godot$ chmod +x Godot.app/Contents/MacOS/Godot
 
-Compiling for 32 and 64-bit
----------------------------
-
-All macOS versions after 10.6 are 64-bit exclusive, so the executable
-will be a ".64" file by default for most users. If you would like to
-compile a ".fat" executable which contains both 32 and 64-bit code,
-you can do so by specifying the bits in the scons command like so:
-
-::
+Cross-compiling for macOS from Linux
+------------------------------------
 
-    user@host:~/godot$ scons platform=osx bits=fat
+It is possible to compile for macOS in a Linux environment (and maybe also in
+Windows using the Windows Subsystem for Linux). For that, you'll need to install
+`OSXCross <https://github.com/tpoechtrager/osxcross>`__ to be able to use macOS
+as a target. First, follow the instructions to install it:
 
-Cross-compiling
----------------
+Clone the `OSXCross repository <https://github.com/tpoechtrager/osxcross>`__
+somewhere on your machine (or download a ZIP file and extract it somewhere),
+e.g.::
 
-It is possible to compile for macOS in a Linux environment (and maybe
-also in Windows with Cygwin). For that you will need
-`OSXCross <https://github.com/tpoechtrager/osxcross>`__ to be able
-to use macOS as target. First, follow the instructions to install it:
-
-Clone the `OSXCross repository <https://github.com/tpoechtrager/osxcross>`
-somewhere on your machine (or download a zip file and extract it somewhere),
-e.g.:
-
-::
-
-    user@host:~$ git clone https://github.com/tpoechtrager/osxcross.git /home/myuser/sources/osxcross
+    user@host:~$ git clone --depth=1 https://github.com/tpoechtrager/osxcross.git "$HOME/osxcross"
 
 1. Follow the instructions to package the SDK:
    https://github.com/tpoechtrager/osxcross#packaging-the-sdk
@@ -78,20 +69,14 @@ e.g.:
 
 After that, you will need to define the ``OSXCROSS_ROOT`` as the path to
 the OSXCross installation (the same place where you cloned the
-repository/extracted the zip), e.g.:
+repository/extracted the zip), e.g.::
 
-::
+    user@host:~$ export OSXCROSS_ROOT="$HOME/osxcross"
 
-    user@host:~$ export OSXCROSS_ROOT=/home/myuser/sources/osxcross
-
-Now you can compile with SCons like you normally would:
-
-::
+Now you can compile with SCons like you normally would::
 
     user@host:~/godot$ scons platform=osx
 
-If you have an OSXCross SDK version different from the one expected by the SCons buildsystem, you can specify a custom one with the ``osxcross_sdk`` argument:
-
-::
+If you have an OSXCross SDK version different from the one expected by the SCons buildsystem, you can specify a custom one with the ``osxcross_sdk`` argument::
 
     user@host:~/godot$ scons platform=osx osxcross_sdk=darwin15