[Xamarin.Android.Build.Tasks] remove Xamarin.Android.Windows.targets

[jonathanpeppers]

Fixes: http://work.devdiv.io/707557

In 539954c, I was aiming to remove the
_RegisterAndroidFilesWithFileWrites MSBuild target (runs only on
Windows). I was having trouble getting everything to work, so I undid
this change to make the PR smaller.

Reasons to remove _RegisterAndroidFilesWithFileWrites:

• It looks like it may be a source of incremental build bugs. It
  causes $(CleanFile) to grow on incremental builds indefinitely...
• We should instead use the FileWrites item group appropriately.
• We can avoid ~81ms of build time.

81 ms  _RegisterAndroidFilesWithFileWrites        1 calls

Revisiting it now, it looks like we can remove
Xamarin.Android.Windows.targets completely!

• _RegisterAndroidFilesWithFileWrites is the only target.
• The $(_IsRunningXBuild) property is only used in this file.
• I moved the $(Debugger) property to
  Xamarin.Android.Common.props. I believe this value is only used in
  VS Windows, but it make more sense to be here.

CopyGeneratedJavaResourceClasses

The <CopyGeneratedJavaResourceClasses/> MSBuild task was copying an
R.java file from %TEMP% to:

$(IntermediateOutputPath)android\unnamedproject\unnamedproject\R.java

We only use this file in one place, since the rest of the build uses:

$(IntermediateOutputPath)android\src\unnamedproject\unnamedproject\R.java

We can avoid copying this extra file and adding it to FileWrites:

• <CopyGeneratedJavaResourceClasses/> now optionally uses the
  DestinationTopDirectory property
• If DestinationTopDirectory is blank, the original source file is
  returned as the PrimaryJavaResgenFile output property.

We now use the R.java from %TEMP% directly, and avoid copying a
file to $(IntermediateOutputPath).

Other Changes

I modified the CheckNothingIsDeletedByIncrementalClean test to
verify that $(CleanFile) isn't growing on incremental builds.

Anything added to FileWrites during the _CompileDex MSBuild target
(or its dependent targets) wasn't showing up in $(CleanFile)! I
adjusted its BeforeTargets to match what I did in 539954c for
_PrepareAssemblies.

Two files needed to be added to FileWrites:

• $(_PackagedResources)
• $(_GeneratedPrimaryJavaResgenFile)

[jonathanpeppers]

Need to look into test failures.

[jonathanpeppers]

@dellis1972 I need to ask you about this after the break: https://github.com/xamarin/xamarin-android/blob/46f02511f8c91b133fb09fdcad2fa8fe9f2cc730/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets#L1795-L1801

This task creates $(IntermediateOutputPath)android\unnamedproject\unnamedproject\R.java, but I normally expect this file in $(IntermediateOutputPath)android\src\unnamedproject\unnamedproject\R.java.

Is this path wrong, or are we deliberately keeping two copies? I'm seeing the one not in src getting deleted by IncrementalClean.

[dellis1972]

@jonathanpeppers we need to figure out where that $(IntermediateOutputPath)android\unnamedproject\unnamedproject\R.java is being used.. If its a .java file it should be in src afaik.

[jonathanpeppers]

@dellis1972 it looks like the only thing using this file: $(IntermediateOutputPath)android\unnamedproject\unnamedproject\R.java

Is the <GenerateResourceDesigner/> task right below it using $(_GeneratedPrimaryJavaResgenFile):
https://github.com/xamarin/xamarin-android/blob/d1a307097419aa80608ee3636bc9f30aa6860f75/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets#L1263-L1277

It looks like:

• <Aapt/> puts R.java in %TEMP%
• <CopyGeneratedJavaResourceClasses/> finds it in %TEMP% and copies to $(IntermediateOutputPath)android\unnamedproject\unnamedproject\R.java
• <GenerateResourceDesigner/> uses $(IntermediateOutputPath)android\unnamedproject\unnamedproject\R.java
• <RemoveDirFixed/> deletes the temp dir

I'm thinking I could just rework this to use the R.java directly from %TEMP%? And not copy anything?