initial steps for including symbols

@ahelwer - seems several steps are involved for enableing snupkg. I will try to see if I can get there. The NugetCommand@2 specifies whether to include symbols, but I haven't found the portion where it allows the user to specify the name of the package (to snukpg instead of nupkg).

scripts/nightly.yaml

@@ -1,12 +1,12 @@
 variables:
-  z3Version: '4.8.7'
+  z3Version: '4.9.10'
 
 jobs:
 
 - job: Mac
   displayName: "Mac Build"
   pool:
-    vmImage: "macOS-10.14"
+    vmImage: "macOS-latest"
   steps:
   - script: python scripts/mk_unix_dist.py --dotnet-key=$(Build.SourcesDirectory)/resources/z3.snk
   - script: git clone https://github.com/z3prover/z3test z3test
@@ -20,7 +20,7 @@ jobs:
 - job: Ubuntu
   displayName: "Ubuntu build"
   pool:
-    vmImage: "ubuntu-16.04"
+    vmImage: "ubuntu-latest"
   steps:
   - script: python scripts/mk_unix_dist.py --dotnet-key=$(Build.SourcesDirectory)/resources/z3.snk
   - script: git clone https://github.com/z3prover/z3test z3test
@@ -148,7 +148,7 @@ jobs:
   - Windows64
   - Mac
   pool:
-    vmImage: "ubuntu-16.04"
+    vmImage: "ubuntu-latest"
   steps:
   - task: DownloadPipelineArtifact@0
     inputs: