Mac installation: Add a note to install the command line tools
Mac installation: Add a note to install the command line tools

There are not installed by default anymore in XCode.

Add the link to https://developer.apple.com/xcode/ instead of the
installation out-of-date CD reference.

Change-Id: Icec7b65e28cff8b936364e245c5e102b8e901d15
Reviewed-by: Sean Harmer <dd3a28a27ba8fc1a24091f8e1ee0edededfbc9cc@kdab.com>

kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc