[One .NET] fix duplicate .pdb files for multiple RIDs

[jonathanpeppers]

Deploying a project that uses two $(RuntimeIdentifiers) will fail on
our new fast deploy system with:

Xamarin.Android.Common.Debugging.targets(589,5): Access to the path 'obj/Debug/net5.0-android/android/assets/' is denied.
    at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String path, OpenFlags flags, Int32 mode)
    at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options)
    at Xamarin.Android.Tasks.FastDeploy.DeployFileWithFastDevTool(ITaskItem file, String toolPath, String overridePath, Byte[] buffer, Byte[] compressed, LZ4Level lz4level) in /Users/builder/azdo/_work/18/s/xamarin-android/external/monodroid/tools/msbuild/Tasks/FastDeploy.cs:line 579
    at Xamarin.Android.Tasks.FastDeploy.DeployFastDevFiles(String toolPath, String overridePath) in /Users/builder/azdo/_work/18/s/xamarin-android/external/monodroid/tools/msbuild/Tasks/FastDeploy.cs:line 491
    at Xamarin.Android.Tasks.FastDeploy.RunTaskAsync() in /Users/builder/azdo/_work/18/s/xamarin-android/external/monodroid/tools/msbuild/Tasks/FastDeploy.cs:line 175

Reviewing the log, there are some weird things happening. Some
incorrect @(_ResolvedSymbols) items are passed to the
<FastDeploy/> MSBuild task:

_ResolvedSymbols
    obj/Debug/net5.0-android/android/assets/
    obj/Debug/net5.0-android/android/assets/

This is caused by the contents of the @(ResolvedFileToPublish) item
group that is populated by the ComputeFilesToPublish MSBuild target
in the dotnet/sdk:

ResolvedFileToPublish
    obj/Debug/net5.0-android/HelloForms.dll
    obj/Debug/net5.0-android/android.21-arm64/HelloForms.pdb
    obj/Debug/net5.0-android/android.21-x86/HelloForms.pdb

The HelloForms.pdb files listed here do not actually exist, the
path should be: obj/Debug/net5.0-android/HelloForms.pdb.
This is caused by the way our "outer" build has no $(RuntimeIdentifer),
while we have an "inner" build that runs per-RID.

The "inner" build needs to fix up the @(_DebugSymbolsIntermediatePath)
item group to account for this:

https://github.com/dotnet/sdk/blob/ee455863aa6ddf13108bb54b37a5a47fb12fe39e/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Publish.targets#L522-L555

We were already fixing up @(IntermediateAssembly).

When HelloForms.dll did not map to a single HelloForms.pdb, the
%(DestinationSubPath) item metadata is not added by the
<ProcessAssemblies/> MSBuild task in Xamarin.Android.

And so the following item transform generated an incorrect result:

<_ResolvedSymbols Include="@(ResolvedSymbols->'$(MonoAndroidIntermediateAssemblyDir)%(DestinationSubPath)')" />

To fix this:

• @(_ResolvedSymbols) should check if %(DestinationSubPath) is blank.
• Call ->Distinct() on input to the <ProcessAssemblies/> MSBuild task.
• Patch up the @(_DebugSymbolsIntermediatePath) item group, so that
  it uses the proper value for @(IntermediateOutputPath) of the
  outer build.

See dotnet/msbuild for the definition of @(_DebugSymbolsIntermediatePath): https://github.com/dotnet/msbuild/blob/65d31a0151b072b910d9ea16e152265d467e3239/src/Tasks/Microsoft.Common.CurrentVersion.targets#L374

After these changes, the @(ResolvedFileToPublish) item group appears
correct now:

ResolvedFileToPublish
    obj/Debug/net5.0-android/HelloForms.dll
    obj/Debug/net5.0-android/HelloForms.pdb

HelloForms.pdb now makes it to the .apk file as well.

Other changes:

• Updated a test to look for UnnamedProject.pdb during a multiple
  RID build.
• I removed the Removing duplicate: ... log message, as it was
  printing hundreds of log messages that aren't particularly useful.

[jonpryor]

Is @(_ResolvedAssemblyFiles->Distinct()) potentially stored in a file anywhere? Presumably this expression controls @(_ProcessedShrunkAssemblies)? .Distinct() may change the ordering, and I don't know if that ordering is consistent from one process run to the next, so if this is "somehow" stored in a file anywhere, it may result in bad dependency tracking.

[jonathanpeppers]

->Distinct() in MSBuild preserves ordering, I asked Rainer about this before:

https://github.com/dotnet/msbuild/blob/6605cdf6e969fa670bab736a0aca415da2080cdb/src/Build/Evaluation/Expander.cs#L2517-L2555

@(_ResolvedAssemblyFiles) won't be used anywhere else, but the outputs of <ProcessAssemblies/> will be.

[jonathanpeppers]

@jonpryor I put several more details in the PR text above we can use in the final commit message. If I end up making another change, I'll copy it to the commit message.