FastUpToDate broken with GeneratePackageOnBuild+SuggestedBindingRedirects

[xen2]

GenerateBindingRedirects is always executed due to SuggestedBindingRedirects not being a file.
This doesn't work well with GeneratePackageOnBuild since this target is called again during Pack and changing .config file timestamp.

Steps to reproduce

Project file

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFrameworks>netcoreapp3.1</TargetFrameworks>
    <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Build.Locator" Version="1.2.6" />
  </ItemGroup>

</Project>

Run build in VS multiple times.
UpToDate check fails with:

1>FastUpToDate: Checking copied output (UpToDateCheckBuilt with Original property) file 'C:\Users\xen\source\repos\ConsoleAppFUTD\ConsoleAppFUTD\obj\Debug\netcoreapp3.1\ConsoleAppFUTD.dll.config': (ConsoleAppFUTD)
1>FastUpToDate:     Source 2020-06-05 11:49:36: 'C:\Users\xen\source\repos\ConsoleAppFUTD\ConsoleAppFUTD\obj\Debug\netcoreapp3.1\ConsoleAppFUTD.dll.config'. (ConsoleAppFUTD)
1>FastUpToDate:     Destination 2020-06-05 11:49:35: 'C:\Users\xen\source\repos\ConsoleAppFUTD\ConsoleAppFUTD\bin\Debug\netcoreapp3.1\ConsoleAppFUTD.dll.config'. (ConsoleAppFUTD)

Investigation

GenerateBindingRedirects is run a second time during Pack step:

The .config file is being written a second time in the obj folder after having it's been copied from obj the bin folder during the previous Build step. This results in wrong timestamps for next build/fast-up-to-date check.

It can't even be skipped because the GenerateBindingRedirects target contains SuggestedBindingRedirects in its list of Target.Inputs, and those items are assemblynames instead of files. As a result, the target Inputs/Outputs check will always fail.

https://github.com/microsoft/msbuild/blob/dc485bce3427e9d2b020ce61c2400e7b5a76062c/src/Tasks/Microsoft.Common.CurrentVersion.targets#L2194

Expected behavior

FastUpToDate check work and build is skipped

Actual behavior

FastUpToDate check doesn't work

Environment data

msbuild /version output:

OS info: Windows 10

If applicable, version of the tool that invokes MSBuild (Visual Studio, dotnet CLI, etc):
Visual Studio 16.6.0

[rainersigwald]

GenerateBindingRedirects is run a second time during Pack step:

This seems like the heart of the immediate problem. Not sure if the fix is here or in dotnet/sdk; we'll investigate.

It can't even be skipped because the GenerateBindingRedirects target contains SuggestedBindingRedirects in its list of Target.Inputs, and those items are assemblynames instead of files. As a result, the target Inputs/Outputs check will always fail.

This also seems completely bogus. Let's see if we can figure out why that was (to make sure it wasn't a good idea for some reason) and then fix it.

[KirillOsenkov]

Potentially related: #9337