[Xamarin.Android.Tools.Bytecode] Fix the build

The cherry-pick of commit 439bd83 on master as fe7421d on d16-5
broke the d16-5 build, because 439bd83 occurred *after* ff3081d,
which migrated `Xamarin.Android.Tools.Bytecode.csproj` to an
SDK-style/short-form project, and thus the added file
`KotlinUtilities.cs` was implicitly included in the master build, but
was *not* included in the d16-5 build.  The result was a build break:

	Kotlin/KotlinFixups.cs(35,26): error CS1061: 'ClassAccessFlags' does not
	contain a definition for 'IsPubliclyVisible' and no accessible extension
	method 'IsPubliclyVisible' accepting a first argument of type
	'ClassAccessFlags' could be found (are you missing a using directive or
	an assembly reference?)

Explicitly add `KotlinUtilities.cs` to
`Xamarin.Android.Tools.Bytecode.csproj` so that it now builds.

Author: jonpryor

src/Xamarin.Android.Tools.Bytecode/Xamarin.Android.Tools.Bytecode.csproj

@@ -54,6 +54,7 @@
     <Compile Include="Kotlin\KotlinFixups.cs" />
     <Compile Include="Kotlin\KotlinMetadata.cs" />
     <Compile Include="Kotlin\KotlinProtobufDefinition.cs" />
+    <Compile Include="Kotlin\KotlinUtilities.cs" />
     <Compile Include="Kotlin\PartialStream.cs" />
     <Compile Include="StreamCoda.cs" />
     <Compile Include="Interfaces.cs" />