Fix crashing on startup (#1596)

[wjk]

I have put the currently broken code under #if !CORERT, as suggested by @jkotas. I have also added a TODO comment with a link to issue #1596, which discusses the context for this change.

[wjk]

@jkotas @dnfclas tells me I must sign the CLA, but has provided no link for me to do so (just the label stating that doing so is required). Any pointers?

[jkotas]

The details about CLA are at the end of https://github.com/dotnet/coreclr/blob/master/Documentation/project-docs/contributing.md

I will look into adding this link to the front page to make it more discoverable.

[jkotas]

The change looks good. Thanks!

[dnfclas]

@wjk, Thanks for signing the contribution license agreement so quickly! Actual humans will now validate the agreement and then evaluate the PR.

Thanks, DNFBOT;