[tools] Compute the llvm output file and pass it to the AOT compiler / native linker

dotnet/targets/Xamarin.Shared.Sdk.targets

@@ -738,6 +738,7 @@
 		<ItemGroup Condition="'$(IsMacEnabled)' == 'true'">
 			<!-- Add the AOT-compiled output to the main executable -->
 			<_XamarinMainLibraries Include="@(_AssembliesToAOT -> '%(ObjectFile)')" />
+			<_XamarinMainLibraries Include="@(_AssembliesToAOT -> '%(LLVMFile)')" />
 
 			<!-- copy the aotdata files to the .app -->
 			<ResolvedFileToPublish Include="%(_AssembliesToAOT.AOTData)" >

tools/dotnet-linker/Steps/ComputeAOTArguments.cs

@@ -36,9 +36,7 @@ namespace Xamarin.Linker {
 					var arch = abi.AsArchString ();
 					var aotAssembly = Path.Combine (outputDirectory, arch, Path.GetFileName (input) + ".s");
 					var aotData = Path.Combine (outputDirectory, arch, Path.GetFileNameWithoutExtension (input) + ".aotdata");
-					var llvmFile = string.Empty;
-					if ((abi & Abi.LLVM) == Abi.LLVM)
-						throw ErrorHelper.CreateError (99, $"Support for LLVM hasn't been implemented yet.");
+					var llvmFile = Configuration.Application.IsLLVM ? Path.Combine (outputDirectory, arch, Path.GetFileName (input) + ".llvm.o") : string.Empty;
 					var objectFile = Path.Combine (outputDirectory, arch, Path.GetFileName (input) + ".o");
 					app.GetAotArguments (asm.FullPath, abi, outputDirectory, aotAssembly, llvmFile, aotData, out var processArguments, out var aotArguments, Path.GetDirectoryName (Configuration.AOTCompiler));
 					item.Metadata.Add ("Arguments", StringUtils.FormatArguments (aotArguments));
@@ -47,6 +45,7 @@ namespace Xamarin.Linker {
 					item.Metadata.Add ("Arch", arch);
 					item.Metadata.Add ("AOTData", aotData);
 					item.Metadata.Add ("AOTAssembly", aotAssembly);
+					item.Metadata.Add ("LLVMFile", llvmFile);
 					item.Metadata.Add ("ObjectFile", objectFile);
 				}