Add workaround to make crustup work in Rakudo > 2016.11

[astj]

ref: https://rt.perl.org/Public/Bug/Display.html?id=130535

Currently we cannot run crustup in rakudo > 2016.11. I know this patch is ugly, but at least it works.

[moznion]

Looks good. It is better to work than not work. Could you add a pointer to this pull-request into comment?

[astj]

@moznion Thank you. I added the pointer on https://github.com/tokuhirom/p6-Crust/pull/85/commits/00366d5f7e7ac1901d2a74b1bd7c1fa2611bb6ac !

[tokuhirom]

Great