Ensure context is not cached before logging info

Fixes dotnet#6436 which causes this crash in cases where MSBuild's result
caching is turned on (generally this is for large builds in 32-bit
MSBuild).

```
MSBUILD : error MSB1025: An internal failure occurred while running MSBuild.
Microsoft.Build.Shared.InternalErrorException: MSB0001: Internal MSBuild Error: We shouldn't be accessing the ProjectInstance when the configuration is cached.
   at Microsoft.Build.Shared.ErrorUtilities.ThrowInternalError(String message, Exception innerException, Object[] args)
   at Microsoft.Build.BackEnd.BuildRequestConfiguration.get_Project()
   at Microsoft.Build.BackEnd.Logging.NodeLoggingContext.LogProjectStarted(BuildRequest request, BuildRequestConfiguration configuration)
   at Microsoft.Build.BackEnd.Logging.NodeLoggingContext.LogRequestHandledFromCache(BuildRequest request, BuildRequestConfiguration configuration, BuildResult result)
   at Microsoft.Build.BackEnd.Scheduler.LogRequestHandledFromCache(BuildRequest request, BuildResult result)
   at Microsoft.Build.BackEnd.Scheduler.HandleRequestBlockedByNewRequests(SchedulableRequest parentRequest, BuildRequestBlocker blocker, List`1 responses)
   at Microsoft.Build.BackEnd.Scheduler.ReportRequestBlocked(Int32 nodeId, BuildRequestBlocker blocker)
   at Microsoft.Build.Execution.BuildManager.HandleNewRequest(Int32 node, BuildRequestBlocker blocker)
   at Microsoft.Build.Execution.BuildManager.ProcessPacket(Int32 node, INodePacket packet)
   at Microsoft.Build.Execution.BuildManager.<>c__DisplayClass76_0.<Microsoft.Build.BackEnd.INodePacketHandler.PacketReceived>b__0()
   at Microsoft.Build.Execution.BuildManager.ProcessWorkQueue(Action action)
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.Build.Execution.BuildManager.EndBuild()
```

src/Build/BackEnd/Components/Logging/NodeLoggingContext.cs

@@ -69,7 +69,13 @@ internal ProjectLoggingContext LogProjectStarted(BuildRequestEntry requestEntry)
         internal ProjectLoggingContext LogProjectStarted(BuildRequest request, BuildRequestConfiguration configuration)
         {
             ErrorUtilities.VerifyThrow(this.IsValid, "Build not started.");
-            return new ProjectLoggingContext(this, request, configuration.ProjectFullPath, configuration.ToolsVersion, request.ParentBuildEventContext, configuration.Project?.EvaluationId ?? BuildEventContext.InvalidEvaluationId);
+
+            // If we can retrieve the evaluationId from the project, do so. Don't if it's not available or
+            // if we'd have to retrieve it from the cache in order to access it.
+            // Order is important here because the Project getter will throw if IsCached.
+            int evaluationId = (configuration != null && !configuration.IsCached && configuration.Project != null) ? configuration.Project.EvaluationId : BuildEventContext.InvalidEvaluationId;
+
+            return new ProjectLoggingContext(this, request, configuration.ProjectFullPath, configuration.ToolsVersion, request.ParentBuildEventContext, evaluationId);
         }
 
         /// <summary>