[Xamarin.Android.Build.Tasks] deletebinobj fix for resources

Fixes: #2193

I have been able to reproduce a #deletebinobj bug with the following
steps:
1. `File | New Project | Android App (Xamarin) | Tabbed App`, set
   `Minimum Android Version` to `Android 5.0 (Lollipop)`
2. Build
3. Add a new `TextView` to `Resources\layout\activity_main.axml`, with
   an id of `textView1`
4. Build and Deploy

Get a crash at runtime:

    Android.Views.InflateException: Binary XML file line #1: Error inflating class android.support.design.widget.BottomNavigationView occurred

A `Rebuild` fixes the problem, and the app starts correctly again.

After comparing `obj` directories from before and after, I noticed
`obj\Debug\android\src\android\support\compat\R.java` was missing the
field for `R.id.textView1`!

    public static int textView1=0x7f080091;

This doesn't match the error message we are getting here at all... But
this file is updated by the `_GenerateJavaDesignerForComponent`
MSBuild target. Further research showed that this target was getting
skipped at step no. 4 above, because it was found to be up to date
according to its inputs and outputs.

To verify this was the case, I could delete
`obj\Debug\Component.R.cs.flag` which would also resolve the runtime
exception (instead of a full `Rebuild`).

First, I created a new test:
- `CustomViewAddResourceId` builds a project with
  `<android.support.design.widget.BottomNavigationView />`
- Adds a `textView1` layout, builds again
- Verifies that `obj\Debug\android\src\android\support\compat\R.java`
  contains `textView1`

To fix the problem, I did the following:
- Added `$(_AndroidResgenFlagFile)` as an input to
  `_GenerateJavaDesignerForComponent`, so it will run again when
  `_UpdateAndroidResgen` runs
- Removed
  `AndroidComponentResgenFlagFile="$(_AndroidComponentResgenFlagFile)"`
  from the call to the `<Aapt />` MSBuild task, so it will re-run
  `aapt` and generate `R.java`.

However, things are still breaking when `$(AndroidUseAapt2)` is
enabled. Removing `AndroidComponentResgenFlagFile` from the
`<Aapt2Link />` MSBuild task did not solve the problem here...
I'm not seeing exactly what generates `R.java` when
`$(AndroidUseAapt2)` is enabled? Perhaps another target that calls
`<Aapt2Compile />`?

This PR isn't quite complete until we also get this new test passing
under aapt2.

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/AndroidUpdateResourcesTest.cs

@@ -1372,5 +1372,42 @@ public void LightlyModifyLayout ()
 				Assert.IsFalse (b.Output.IsTargetSkipped ("_UpdateAndroidResgen"), "`_UpdateAndroidResgen` should not be skipped!");
 			}
 		}
+
+		[Test]
+		public void CustomViewAddResourceId ([Values (false, true)] bool useAapt2)
+		{
+			var proj = new XamarinAndroidApplicationProject ();
+			proj.SetProperty ("AndroidUseAapt2", useAapt2.ToString ());
+			proj.LayoutMain = proj.LayoutMain.Replace ("</LinearLayout>", "<android.support.design.widget.BottomNavigationView android:id=\"@+id/navigation\" /></LinearLayout>");
+			proj.Packages.Add (KnownPackages.Android_Arch_Core_Common_26_1_0);
+			proj.Packages.Add (KnownPackages.Android_Arch_Lifecycle_Common_26_1_0);
+			proj.Packages.Add (KnownPackages.Android_Arch_Lifecycle_Runtime_26_1_0);
+			proj.Packages.Add (KnownPackages.AndroidSupportV4_27_0_2_1);
+			proj.Packages.Add (KnownPackages.SupportCompat_27_0_2_1);
+			proj.Packages.Add (KnownPackages.SupportCoreUI_27_0_2_1);
+			proj.Packages.Add (KnownPackages.SupportCoreUtils_27_0_2_1);
+			proj.Packages.Add (KnownPackages.SupportDesign_27_0_2_1);
+			proj.Packages.Add (KnownPackages.SupportFragment_27_0_2_1);
+			proj.Packages.Add (KnownPackages.SupportMediaCompat_27_0_2_1);
+			proj.Packages.Add (KnownPackages.SupportV7AppCompat_27_0_2_1);
+			proj.Packages.Add (KnownPackages.SupportV7CardView_27_0_2_1);
+			proj.Packages.Add (KnownPackages.SupportV7MediaRouter_27_0_2_1);
+			proj.Packages.Add (KnownPackages.SupportV7RecyclerView_27_0_2_1);
+			using (var b = CreateApkBuilder (Path.Combine ("temp", TestName))) {
+				Assert.IsTrue (b.Build (proj), "first build should have succeeded");
+
+				//Add a new android:id
+				var textView1 = "textView1";
+				proj.LayoutMain = proj.LayoutMain.Replace ("</LinearLayout>", $"<TextView android:id=\"@+id/{textView1}\" /></LinearLayout>");
+				proj.Touch (@"Resources\layout\Main.axml");
+
+				Assert.IsTrue (b.Build (proj, doNotCleanupOnUpdate: true), "second build should have succeeded");
+
+				var r_java = Path.Combine (Root, b.ProjectDirectory, proj.IntermediateOutputPath, "android", "src", "android", "support", "compat", "R.java");
+				FileAssert.Exists (r_java);
+				var r_java_contents = File.ReadAllLines (r_java);
+				Assert.IsTrue (StringAssertEx.ContainsText (r_java_contents, textView1), $"android/support/compat/R.java should contain `{textView1}`!");
+			}
+		}
 	}
 }

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

@@ -1526,7 +1526,7 @@ because xbuild doesn't support framework reference assemblies.
 </PropertyGroup>
 
 <Target Name="_GenerateJavaDesignerForComponent"
-  Inputs="@(_AdditonalAndroidResourceCacheFiles);@(_LibraryResourceDirectoryStamps)"
+  Inputs="@(_AdditonalAndroidResourceCacheFiles);@(_LibraryResourceDirectoryStamps);$(_AndroidResgenFlagFile)"
   Outputs="$(_AndroidComponentResgenFlagFile)"
   DependsOnTargets="$(_GenerateJavaDesignerForComponentDependsOnTargets)">
 
@@ -1545,7 +1545,6 @@ because xbuild doesn't support framework reference assemblies.
    ResourceDirectory="$(MonoAndroidResDirIntermediate)"
    AdditionalResourceDirectories="@(LibraryResourceDirectories)"
    AdditionalAndroidResourcePaths="@(_AdditonalAndroidResourceCachePaths)"
-   AndroidComponentResgenFlagFile="$(_AndroidComponentResgenFlagFile)"
    ToolPath="$(AaptToolPath)"
    ToolExe="$(AaptToolExe)"
    ApiLevel="$(_AndroidTargetSdkVersion)"