On WoA, x86 process failed to inject x64 libraries to x64 process

Describe the bug
Currently Detours users should call DetourUpdateProcessWithDll + DetourProcessViaHelperDllsW to inject dlls into target processes. DetourUpdateProcessWithDll is called to injection dlls to the target process with the same arch of the current process. And I've confirmed a x64 process can call DetourUpdateProcessWithDll directly to inject dlls to a64 process, and vice versa. If DetourUpdateProcessWithDll failed, the users should call DetourProcessViaHelperDllsW to start a helper process "rundll32.exe" with the same arch of the target process, and call DetourUpdateProcessWithDll in the helper process.
On WoA, x64 / a64 process can start C:\Windows\SysWOW64\rundll32.exe to be the x86 helper process. And x86 process can start C:\Windows\System32\rundll32.exe to be a64 helper process. However x86 process failed to start a x64 helper process.

The "C:\Windows\System32\rundll32.exe" is an arm64x executable which can be start with arm64 process or x64 process. By default a x64 process starts rundll32.exe, the process will be x64 and an a64 process starts an a64 process. But a x86 process will always starts a64 process. If I need to start a x64 process I need to run "cmd.exe /C start /machine:amd64 rundll32.exe ...", but this is not what DetourProcessViaHelperDllsW does and won't fix my problem because what I started with CREATED_SUSPENDED flag is the cmd process instead of the rundll32 process.

Based on code analysis I see DetourProcessViaHelperDllsW always uses the first dll path in argument rlpDlls. I think a proper fix would be to keep rlpDlls containing x64 dll paths to be written to the payload, but set an a64 dll path to be loaded by rundll32.exe. (This is a possible fix and I have tested it worked for me)

Start at DetourProcessViaHelperDllsW and trace how it selects the first path in rlpDlls and launches rundll32.exe. Reproduce the WoA case where an x86 process requests an x64 helper, then verify that the helper architecture and DLL loaded by rundll32.exe match the target process while the x64 DLL paths remain in the payload.