Ensure that assembly constants are used during pack step.

ci/steps-build-core.yml

@@ -24,4 +24,5 @@ steps:
     versioningScheme: $(VersioningScheme)
     majorVersion: $(Build.Major)
     minorVersion: $(Build.Minor)
-    patchVersion: $(Build.Patch)
+    patchVersion: $(Build.Patch)
+    arguments: '/p:DefineConstants=$(Assembly.Constants)'