Add stdout redirection option to ILCompiler

[MichalPetryka]

The SDK does not expose the stdout from ILC anywhere, add a flag to allow saving it to file instead.

Similar to JitStdOutFile.

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).
13 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to this area: @agocke, @dotnet/ilc-contrib
See info in area-owners.md if you want to be subscribed.

[jkotas]

This looks odd to me as a compiler command line option. Does any other compiler you are aware of have a command line option like this?

[MichalPetryka]

This looks odd to me as a compiler command line option. Does any other compiler you are aware of have a command line option like this?

The JIT has DOTNWT_JitStdOutFile to deal with this issue, vcpkg always redirects compiler output to files, but I am not aware of any other cases.
MSVC and LINK.exe rely on MSBuild piping their outputs, IL2CPP pipes output from compiler to its stdout AFAIR.

EDIT: I'd be fine if instead we had some flag to pipe stdout through the sdk but that seems like a bigger ask.

[teo-tsirpanis]

The SDK does not expose the stdout from ILC anywhere

Doesn't it show up on binlogs? The Exec task has a ConsoleOutput output item.