[Bug c/66066] [6 Regression] r222889 causes bogus error: initializer element is not constant

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66066

--- Comment #15 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Created attachment 35534
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35534&action=edit
gcc6-pr66066

Untested patch without a test