The implement of darwinSupportsAVX512 has been removed in CL 361255.
But the command "go install -buildmode=shared std" failed because the
declaration of it is remained in cpu/cpu_gc_x86.go. It should be removed.
Reviewed-by: Tobias Klauser <firstname.lastname@example.org>
Reviewed-by: Keith Randall <email@example.com>
Run-TryBot: Tobias Klauser <firstname.lastname@example.org>
TryBot-Result: Gopher Robot <email@example.com>
Trust: Ian Lance Taylor <firstname.lastname@example.org>