Fix building the nativeaot project in VS (#121946)

The build doesn't work unless VS knows about the generators in the SLNX.

Author: MichalStrehovsky

src/coreclr/nativeaot/nativeaot.slnx

@@ -10,9 +10,15 @@
     <Platform Name="x86" />
   </Configurations>
   <Folder Name="/gen/">
+    <Project Path="../../libraries/System.Private.CoreLib/gen/EventSourceGenerator.csproj">
+      <BuildType Solution="Checked|*" Project="Debug" />
+    </Project>
     <Project Path="../../libraries/System.Private.CoreLib/gen/System.Private.CoreLib.Generators.csproj">
       <BuildType Solution="Checked|*" Project="Debug" />
     </Project>
+    <Project Path="../../libraries/System.Runtime.InteropServices/gen/DownlevelLibraryImportGenerator/DownlevelLibraryImportGenerator.csproj">
+      <BuildType Solution="Checked|*" Project="Debug" />
+    </Project>
     <Project Path="../../libraries/System.Runtime.InteropServices/gen/LibraryImportGenerator/LibraryImportGenerator.csproj">
       <BuildType Solution="Checked|*" Project="Debug" />
     </Project>