Add OutputType to ILAsm.csproj

src/Tools/ILAsm/ILAsm.csproj

@@ -5,6 +5,7 @@
   <PropertyGroup>
     <TargetFramework>netcoreapp2.0</TargetFramework>
     <RuntimeIdentifiers>$(RoslynPortableRuntimeIdentifiers)</RuntimeIdentifiers>
+    <OutputType>Library</OutputType>
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.NETCore.App" Version="$(MicrosoftNETCoreAppVersion)" />