Build - update macOS build instructions

We no longer need to explicitly install SuperCollider or Erlang as they are now included as prebuilt binaries on the tree. Also the version of Ruby shipping with Catalina works just fine so there's no need to install the latest Ruby just for the purposes of building on user's personal machines (however, the releases will likely continue to ship with their own internal Ruby tracking the latest releases).

Author: samaaron

BUILD-MAC.md

@@ -39,7 +39,7 @@ few dependencies:
 
 1. Xcode (12.1+) and command line tools
 2. Homebrew
-3. All other dependencies - Qt (5.15+), CMake (3.18+), Ruby (2.7.2+), Erlang (23.1+)
+3. All other dependencies - Qt (5.15+), CMake (3.18+)
 
 ### 1.1 Install Xcode
 
@@ -68,16 +68,10 @@ Once you have Homebrew installed, pulling in the rest of the
 dependencies is a couple of lines to execute within a terminal:
 
 ```
-brew install qt cmake ruby erlang 
-brew cask install supercollider
+brew install qt cmake
 
 ```
 
-(Note, if you have already manually installed recent version of
-SuperCollider into your `/Application` folder directly then there's no
-need to `brew cask install supercollider` as this will complain as an
-existing version of the app is already installed).
-
 ## 2. Preparing the Build
 
 Once we have installed all the dependencies, we're almost ready to build