[gn build] Make NOSORT line actually work

GN wants the NOSORT line to be the first line of a comment block, not the last
line.

I sent https://gn-review.googlesource.com/c/gn/+/3560 to support having it in
the last line too, but since it will be a while until everyone has that change
even if it's expected, use the form that works today.

Differential Revision: https://reviews.llvm.org/D56065

llvm-svn: 350060