install xcode sdk on osx not linux

azure-pipelines.yml

@@ -9,11 +9,6 @@ jobs:
       script: |
         sudo apt-get update
         sudo apt-get install castxml
-  - task: CmdLine@2
-    displayName: 'Install OSX Sdk'
-    inputs:
-      script: |
-        ./scripts/XcodeLegacy.sh -osx1013
 
   - task: CmdLine@2
     displayName: 'Install Nuke'
@@ -50,6 +45,12 @@ jobs:
         curl -o ./mono.pkg https://download.mono-project.com/archive/5.18.0/macos-10-universal/MonoFramework-MDK-5.18.0.225.macos10.xamarin.universal.pkg 
         sudo installer -verbose -pkg ./mono.pkg -target /
 
+  - task: CmdLine@2
+    displayName: 'Install OSX Sdk'
+    inputs:
+      script: |
+        ./scripts/XcodeLegacy.sh -osx1013
+
   - task: Xcode@5
     inputs:
       actions: 'build'