`dotnet test` fails to launch `DumpMinitool*.exe` because it is a DLL - doesn't produce dump for process of different architecture

Describe the bug

Running dotnet test with hang dumps enabled does not create a dump for (child) processes that do not match the current architecture (for example, 64-bit testhost, test launches a 32-bit process).

To Reproduce

On Windows x64:

1. dotnet new xunit
2. Add a test that launches a 32-bit process that will stay running:

[Fact]
public void LaunchX86()
{
    using (Process p = Process.Start(@"C:\Windows\SysWOW64\notepad.exe"))
    {
        p.WaitForExit();
    }
}

1. dotnet test --blame-hang-timeout 10s --diag:log.txt;tracelevel=verbose

Expected

Dump to be produced for both testhost and notepad

Actual

No dump for notepad

From log.datacollector:

TpTrace Error: 0 : 19220, 12, 2022/05/13, 15:45:21.877, 2157168736492, datacollector.dll, WindowsHangDumper.Dump: Error dumping process 21596 - notepad: System.ComponentModel.Win32Exception (193): An error occurred trying to start process 'C:\Program Files\dotnet\sdk\7.0.100-preview.3.22179.4\Extensions\DumpMinitool.x86.exe' with working directory 'C:\Users\elfung\AppData\Local\Temp\dd4a4675-188b-417e-9a1d-5c4dc0bf6729'. The specified executable is not a valid application for this OS platform.
   at System.Diagnostics.Process.StartWithCreateProcess(ProcessStartInfo startInfo)
   at Microsoft.VisualStudio.TestPlatform.PlatformAbstractions.ProcessHelper.<>c__DisplayClass1_0.<LaunchProcess>g__InitializeAndStart|0()
   at Microsoft.VisualStudio.TestPlatform.PlatformAbstractions.ProcessHelper.LaunchProcess(String processPath, String arguments, String workingDirectory, IDictionary`2 envVariables, Action`2 errorCallback, Action`1 exitCallBack, Action`2 outputCallBack)
   at Microsoft.TestPlatform.Extensions.BlameDataCollector.WindowsHangDumper.CollectDump(Process process, String outputFile, DumpTypeOption type)
   at Microsoft.TestPlatform.Extensions.BlameDataCollector.WindowsHangDumper.Dump(Int32 processId, String outputDirectory, DumpTypeOption type).

Further technical details

.NET SDK (reflecting any global.json):
 Version:   7.0.100-preview.3.22179.4
 Commit:    c48f2c30ee

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19044
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\7.0.100-preview.3.22179.4\

Apparently the DumpMinitool.x86.exe that is installed is not an executable?

>dumpbin "C:\Program Files\dotnet\sdk\7.0.100-preview.3.22179.4\Extensions\DumpMinitool.x86.exe"
Microsoft (R) COFF/PE Dumper Version 14.33.31424.0
Copyright (C) Microsoft Corporation.  All rights reserved.

Dump of file C:\Program Files\dotnet\sdk\7.0.100-preview.3.22179.4\Extensions\DumpMinitool.x86.exe

File Type: DLL

[AaronRobinsonMSFT]

Should this issue be moved into microsoft/vstest?

I believe @elinor-fung considered this but opted to report it here because when pulling down the assets from microsoft/vstest the binary is correct. Mentioned in https://github.com/dotnet/sdk/issues/25421#issuecomment-1126565424.

[nohwnd]

Fixed in both net7 and net6.0.400.