Merge pull request #9178 from mono/backport-pr-9176-to-master

[master] Set `DesignTimeBuild` when evaluating SourceFiles

Author: sandyarmstrong

main/src/core/MonoDevelop.Core/MonoDevelop.Projects/Project.cs

@@ -782,6 +782,7 @@ public async Task<CoreCompileEvaluationResult> GetItemsFromCoreCompileDependenci
 						ctx.LoadReferencedProjects = false;
 						ctx.BuilderQueue = BuilderQueue.ShortOperations;
 						ctx.LogVerbosity = MSBuildVerbosity.Quiet;
+						ctx.GlobalProperties.SetValue ("DesignTimeBuild", "true");
 
 						var evalResult = await project.RunTargetInternal (monitor, dependsList, config.Selector, ctx);
 						if (evalResult != null && evalResult.Items != null) {