[Xamarin.Android.Build.Tasks] Use a Response file for AOT

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems/edit/609244

Windows has a limit on the length of command line arguments.
As a result AOT can fail on windows if the project paths
are too long.

mono 2018-06 introduced a `--response=FILE` which allows
us to provide all the options in a file rather than on the
command line directly.

src/Xamarin.Android.Build.Tasks/Tasks/Aot.cs

@@ -447,50 +447,58 @@ bool RunAotCompiler (string assembliesPath, string aotCompiler, string aotOption
 		{
 			var stdout_completed = new ManualResetEvent (false);
 			var stderr_completed = new ManualResetEvent (false);
-			var psi = new ProcessStartInfo () {
-				FileName = aotCompiler,
-				Arguments = aotOptions + " " + assembly,
-				UseShellExecute = false,
-				RedirectStandardOutput = true,
-				RedirectStandardError = true,
-				CreateNoWindow=true,
-				WindowStyle=ProcessWindowStyle.Hidden,
-				WorkingDirectory = WorkingDirectory,
-			};
-
-			// we do not want options to be provided out of band to the cross compilers
-			psi.EnvironmentVariables ["MONO_ENV_OPTIONS"] = String.Empty;
-			// the C code cannot parse all the license details, including the activation code that tell us which license level is allowed
-			// so we provide this out-of-band to the cross-compilers - this can be extended to communicate a few others bits as well
-			psi.EnvironmentVariables ["MONO_PATH"] = assembliesPath;
-
-			LogDebugMessage ("[AOT] MONO_PATH=\"{0}\" MONO_ENV_OPTIONS=\"{1}\" {2} {3}",
-				psi.EnvironmentVariables ["MONO_PATH"], psi.EnvironmentVariables ["MONO_ENV_OPTIONS"], psi.FileName, psi.Arguments);
-
-			using (var proc = new Process ()) {
-				proc.OutputDataReceived += (s, e) => {
-					if (e.Data != null)
-						OnAotOutputData (s, e);
-					else
-						stdout_completed.Set ();
-				};
-				proc.ErrorDataReceived += (s, e) => {
-					if (e.Data != null)
-						OnAotErrorData (s, e);
-					else
-						stderr_completed.Set ();
+			var responseFile = Path.GetTempFileName ();
+			try {
+				File.WriteAllText (responseFile, aotOptions + " " + assembly);
+
+				var psi = new ProcessStartInfo () {
+					FileName = aotCompiler,
+					Arguments = $"--response=\"{responseFile}\"",
+					UseShellExecute = false,
+					RedirectStandardOutput = true,
+					RedirectStandardError = true,
+					CreateNoWindow = true,
+					WindowStyle = ProcessWindowStyle.Hidden,
+					WorkingDirectory = WorkingDirectory,
 				};
-				proc.StartInfo = psi;
-				proc.Start ();
-				proc.BeginOutputReadLine ();
-				proc.BeginErrorReadLine ();
-				token.Register (() => { try { proc.Kill (); } catch (Exception) { } });
-				proc.WaitForExit ();
-				if (psi.RedirectStandardError)
-					stderr_completed.WaitOne (TimeSpan.FromSeconds (30));
-				if (psi.RedirectStandardOutput)
-					stdout_completed.WaitOne (TimeSpan.FromSeconds (30));
-				return proc.ExitCode == 0;
+
+				// we do not want options to be provided out of band to the cross compilers
+				psi.EnvironmentVariables ["MONO_ENV_OPTIONS"] = String.Empty;
+				// the C code cannot parse all the license details, including the activation code that tell us which license level is allowed
+				// so we provide this out-of-band to the cross-compilers - this can be extended to communicate a few others bits as well
+				psi.EnvironmentVariables ["MONO_PATH"] = assembliesPath;
+
+				LogDebugMessage ("[AOT] MONO_PATH=\"{0}\" MONO_ENV_OPTIONS=\"{1}\" {2} {3}",
+					psi.EnvironmentVariables ["MONO_PATH"], psi.EnvironmentVariables ["MONO_ENV_OPTIONS"], psi.FileName, psi.Arguments);
+
+				using (var proc = new Process ()) {
+					proc.OutputDataReceived += (s, e) => {
+						if (e.Data != null)
+							OnAotOutputData (s, e);
+						else
+							stdout_completed.Set ();
+					};
+					proc.ErrorDataReceived += (s, e) => {
+						if (e.Data != null)
+							OnAotErrorData (s, e);
+						else
+							stderr_completed.Set ();
+					};
+					proc.StartInfo = psi;
+					proc.Start ();
+					proc.BeginOutputReadLine ();
+					proc.BeginErrorReadLine ();
+					token.Register (() => { try { proc.Kill (); } catch (Exception) { } });
+					proc.WaitForExit ();
+					if (psi.RedirectStandardError)
+						stderr_completed.WaitOne (TimeSpan.FromSeconds (30));
+					if (psi.RedirectStandardOutput)
+						stdout_completed.WaitOne (TimeSpan.FromSeconds (30));
+					return proc.ExitCode == 0;
+				}
+			} finally {
+				if (File.Exists (responseFile))
+					File.Delete (responseFile);
 			}
 		}