Don't specify MainEntryPoint when compiling Razor assembly

Author: pranavkm

src/Microsoft.NET.Sdk.Razor/build/netstandard2.0/Microsoft.NET.Sdk.Razor.Compilation.targets

@@ -42,6 +42,7 @@ Copyright (c) .NET Foundation. All rights reserved.
     Remove @(DocFileItem)
     Remove PdbFile="$(PdbFile)"
     Remove OutputRefAssembly="@(IntermediateRefAssembly)"
+    Remove MainEntryPoint="$(StartupObject)"
 
     Remove EmbedAllSources="$(EmbedAllSources)" - not supported by our supported version of MSBuild
 
@@ -133,7 +134,6 @@ Copyright (c) .NET Foundation. All rights reserved.
          KeyFile="$(KeyOriginatorFile)"
          LangVersion="$(LangVersion)"
          LinkResources="@(LinkResource)"
-         MainEntryPoint="$(StartupObject)"
          ModuleAssemblyName="$(ModuleAssemblyName)"
          NoConfig="true"
          NoLogo="$(NoLogo)"

test/Microsoft.AspNetCore.Razor.Design.Test/IntegrationTests/BuildIntegrationTest.cs

@@ -553,6 +553,21 @@ public async Task Build_WithP2P_WorksWhenBuildProjectReferencesIsDisabled()
             Assert.BuildPassed(result);
         }
 
+        [Fact]
+        [InitializeTestProject("SimpleMvc")]
+        public async Task Build_WithStartupObjectSpecified_Works()
+        {
+            var result = await DotnetMSBuild("Build", $"/p:StartupObject=SimpleMvc.Program");
+
+            Assert.BuildPassed(result);
+
+            Assert.FileExists(result, IntermediateOutputPath, "SimpleMvc.Views.dll");
+            Assert.FileExists(result, IntermediateOutputPath, "SimpleMvc.Views.pdb");
+
+            Assert.FileExists(result, IntermediateOutputPath, "SimpleMvc.Views.dll");
+            Assert.FileExists(result, IntermediateOutputPath, "SimpleMvc.Views.pdb");
+        }
+
         private static DependencyContext ReadDependencyContext(string depsFilePath)
         {
             var reader = new DependencyContextJsonReader();