Update build instructions for 2.3.0

mac/Build.txt

@@ -1,3 +1,5 @@
+Instructions for building on Mac
+
 At this time, Audacity is usually built with the 10.7 SDK.  This is to give
 compatibility with older versions of MacOSX.
 To build Audacity using Xcode 5.1 or newer, you need to extract the 10.7 SDK
@@ -7,10 +9,9 @@ In the instructions below, Xcode 4.3.3 (for the 10.7 SDK) and Xcode 8.1 will
 be used and can be downloaded from https://developer.apple.com/download/more/ 
 (requires Apple ID to login).
 
-Fuller instructions that cover 
+Fuller instructions that include 
    * Using other Xcodes
    * Optional signing of DMGs
-   * Applying wxWidgets patches one by one
 can be found on our wiki at http://wiki.audacityteam.org/wiki/Building_On_Mac
 
 1) Download Xcode 8.1 and install it to /Applications.
@@ -43,9 +44,9 @@ can be found on our wiki at http://wiki.audacityteam.org/wiki/Building_On_Mac
    Don't be tempted to use Widgets already installed by a package manager such 
    as Homebrew because this will cause problems.
 
-   We have applied some Audacity specific patches to the official
-   wxWidgets 3.1.1 branch, found here:
-   https://github.com/audacity/wxWidgets/tree/audacity-fixes-3.1.1
+   As of 16-Apr-2018 we haven't yet applied any Audacity specific patches
+   to the official wxWidgets 3.1.1 branch, so currently it is the same as:
+   https://github.com/audacity/wxWidgets/tree/v3.1.1
 
 9) Change directory to the folder wxWidgets was cloned to then build/install 
     wxWidgets: