set DOTNET_SKIP_FIRST_TIME_EXPERIENCE to true so we don't waste time caching on build agents

.vsts.ix-ci.yml

@@ -13,6 +13,7 @@ trigger:
 queue: Hosted VS2017
 variables: 
   BuildConfiguration: Release
+  DOTNET_SKIP_FIRST_TIME_EXPERIENCE: true
   
 steps:
 - template: .vsts.ix-shared.yml

.vsts.ix-pr.yml

@@ -3,6 +3,7 @@ trigger: none
 queue: Hosted VS2017
 variables: 
   BuildConfiguration: Release
+  DOTNET_SKIP_FIRST_TIME_EXPERIENCE: true
   
 steps:
 - template: .vsts.ix-shared.yml

.vsts.rx-ci.yml

@@ -15,6 +15,7 @@ queue: Hosted VS2017
 variables: 
   BuildConfiguration: Release
   BuildPlatform: Any CPU
+  DOTNET_SKIP_FIRST_TIME_EXPERIENCE: true
     
 steps:
 - template: .vsts.rx-shared.yml

.vsts.rx-pr.yml

@@ -4,6 +4,7 @@ queue: Hosted VS2017
 variables: 
   BuildConfiguration: Release
   BuildPlatform: Any CPU
+  DOTNET_SKIP_FIRST_TIME_EXPERIENCE: true
     
 steps:
 - template: .vsts.rx-shared.yml