Make it so Helix runs can be rerun and preserve history (#10457)

* Make it so Helix runs can be rerun and preserve history

Addresses https://github.com/aspnet/AspNetCore/issues/8235



* Update eng/helix/helix.proj

Co-Authored-By: Nate McMaster <natemcmaster@users.noreply.github.com>

eng/helix/helix.proj

@@ -19,7 +19,7 @@
   <PropertyGroup Condition=" '$(CI)' == 'true' ">
     <HelixType>ci</HelixType>
     <Creator>aspnetcore</Creator>
-    <HelixBuild>$(BUILD_BUILDNUMBER)</HelixBuild>
+    <HelixBuild>$(BUILD_BUILDNUMBER).$([System.DateTime]::Now.ToString('HH.mm'))</HelixBuild>
     <WaitForWorkItemCompletion>true</WaitForWorkItemCompletion>
     <EnableAzurePipelinesReporter>true</EnableAzurePipelinesReporter>
     <FailOnMissionControlTestFailure>true</FailOnMissionControlTestFailure>