[Xamarin.Android.Build.Tasks] Extend the Aot Task to allow the passin…

…g of additional arguments (#185)

Context https://bugzilla.xamarin.com/show_bug.cgi?id=43500

We need a way to pass additional arguments to the aot system.
This is so users can add additional parameters to tweak the
output. In the case of Bug 43500 we needed to be able to pass

	'no-write-symbols' or 'no-debug'

Rather than just hardcoding those values we now provide a

	$(AndroidAotAdditionalArguments)

msbuild property which defaults to empty but users can override
to pass any additional parameters that they need.

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

@@ -60,6 +60,8 @@ public class Aot : Task
 
 		public string AndroidSequencePointsMode { get; set; }
 
+		public string AotAdditionalArguments { get; set; }
+
 		public ITaskItem[] AdditionalNativeLibraryReferences { get; set; }
 
 		[Output]
@@ -317,7 +319,7 @@ bool DoExecute () {
 						Path.GetFileName (assembly.ItemSpec)));
 
 					string aotOptions = string.Format (
-						"{0}--aot={8}{1}outfile={2},asmwriter,mtriple={3},tool-prefix={4},ld-flags={5},llvm-path={6},temp-path={7}",
+						"{0}--aot={9}{8}{1}outfile={2},asmwriter,mtriple={3},tool-prefix={4},ld-flags={5},llvm-path={6},temp-path={7}",
 						EnableLLVM ? "--llvm " : string.Empty,
 						AotMode != AotMode.Normal ? string.Format("{0},", AotMode.ToString().ToLowerInvariant()) : string.Empty,
 						QuoteFileName (outputFile),
@@ -326,7 +328,8 @@ bool DoExecute () {
 						ldFlags,
 						QuoteFileName (SdkBinDirectory),
 						QuoteFileName (outdir),
-						sequencePointsMode == SequencePointsMode.Offline ? string.Format("msym-dir={0},", QuoteFileName(outdir)) : string.Empty
+						sequencePointsMode == SequencePointsMode.Offline ? string.Format("msym-dir={0},", QuoteFileName(outdir)) : string.Empty,
+						AotAdditionalArguments != string.Empty ? string.Format ("{0},", AotAdditionalArguments) : string.Empty
 					);
 
 					// Due to a Monodroid MSBuild bug we can end up with paths to assemblies that are not in the intermediate

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets

@@ -2173,6 +2173,7 @@ because xbuild doesn't support framework reference assemblies.
 	SdkBinDirectory="$(MonoAndroidBinDirectory)"
 	SupportedAbis="$(_BuildTargetAbis)"
 	AndroidSequencePointsMode="$(_SequencePointsMode)"
+	AotAdditionalArguments="$(AndroidAotAdditionalArguments)"
 	ResolvedAssemblies="@(_ResolvedAssemblies)"
 	AotOutputDirectory="$(_AndroidAotBinDirectory)"
 	IntermediateAssemblyDir="$(MonoAndroidIntermediateAssemblyDir)"