Update BUILDING.md

BUILDING.md

@@ -2,7 +2,7 @@
 
 We typically develop against the latest stable version of Xcode.
 
-As of this writing, that's Xcode 10.1
+As of this writing, that's Xcode 11.4
 
 ## Prerequistes
 
@@ -47,15 +47,15 @@ Open the `Signal.xcworkspace` in Xcode.
 open Signal.xcworkspace
 ```
 
-In the TARGETS area of the General tab, change the Team drop down to
-your own. You will need to do that for all the listed targets, for ex. 
+In the TARGETS area of the General tab, change the Team dropdown to
+your own. You will need to do that for all the listed targets, for ex.
 Signal, SignalShareExtension, and SignalMessaging. You will need an Apple
-Developer account for this. 
+Developer account for this.
 
 On the Capabilities tab, turn off Push Notifications and Data Protection,
 while keeping Background Modes on. The App Groups capability will need to
 remain on in order to access the shared data storage. The App ID needs to
-match the SignalApplicationGroup string set in TSConstants.h. 
+match the SignalApplicationGroup string set in TSConstants.h.
 
 If you wish to test the Documents API, the iCloud capability will need to
 be on with the iCloud Documents option selected.
@@ -68,4 +68,3 @@ Features related to push notifications are known to be not working for
 third-party contributors since Apple's Push Notification service pushes
 will only work with Open Whisper Systems production code signing
 certificate.
-