[build] Updated to macOS 10.14

Author: spoenemann

azure-pipelines.yml

@@ -25,7 +25,7 @@ jobs:
         imageName: 'ubuntu-16.04'
         ExecutableSuffix: ''
       mac:
-        imageName: 'macos-10.13'
+        imageName: 'macos-10.14'
         ExecutableSuffix: ''
       windows:
         imageName: 'vs2017-win2016'