Disable signing of non-shipping packages

Also clean up how $(SignCoreSdk) is set so that `build -sign` does so
and allows a full dry run locally.

eng/Signing.props

@@ -0,0 +1,16 @@
+<Project>
+
+  <ItemGroup>
+    <!-- Do not sign non-shipping packages -->
+    <ItemsToSign Remove="$(ArtifactsNonShippingPackagesDir)**\*.nupkg" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <!--
+      Signing of shipping artifacts (layout, msi, bundle) are handled separately.
+      It is therefore expected that above removal can yield an empty set.
+    -->
+    <AllowEmptySignList>true</AllowEmptySignList>
+  </PropertyGroup>
+
+</Project>

eng/setbuildinfo.bat

@@ -27,12 +27,12 @@ IF /I "%Architecture:~0,3%"=="ARM" (
     ECHO ##vso[task.setvariable variable=TestParameter]
     ECHO ##vso[task.setvariable variable=RunTests]false
 
-    ECHO ##vso[task.setvariable variable=AdditionalBuildParameters]/p:SignCoreSdk=true /p:DotNetSignType=%SignType%
 
 ) ELSE (
     ECHO NOT ARM
     ECHO ##vso[task.setvariable variable=TestParameter]-test
     ECHO ##vso[task.setvariable variable=RunTests]true
 
-    ECHO ##vso[task.setvariable variable=AdditionalBuildParameters]-sign /p:SignCoreSdk=true /p:DotNetSignType=%SignType%
 )
+
+ECHO ##vso[task.setvariable variable=AdditionalBuildParameters]-sign /p:DotNetSignType=%SignType%

run-build.ps1

@@ -7,15 +7,21 @@
 param(
     [string]$Configuration="Debug",
     [string]$Architecture="x64",
+    [switch]$Sign=$false,
     [Parameter(ValueFromRemainingArguments=$true)][String[]]$ExtraParameters
 )
 
 $RepoRoot = "$PSScriptRoot"
 
-$ArchitectureParam="/p:Architecture=$Architecture"
+$Parameters = "/p:Architecture=$Architecture"
-$ConfigurationParam="-configuration $Configuration"
+$Parameters = "$Parameters -configuration $Configuration"
+
+if ($Sign) {
+  $Parameters = "$Parameters -sign /p:SignCoreSdk=true"
+}
+
 try {
-    $ExpressionToInvoke = "$RepoRoot\eng\common\build.ps1 -restore -build $ConfigurationParam $ArchitectureParam $ExtraParameters"
+    $ExpressionToInvoke = "$RepoRoot\eng\common\build.ps1 -restore -build $Parameters $ExtraParameters"
     Write-Host "Invoking expression: $ExpressionToInvoke"
     Invoke-Expression $ExpressionToInvoke
 }