[Bug target/78077] gcc 6.2.0 fails to link temacs from emacs-25.1 using the Xcode 8 linker

[howarth.at.gcc at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78077

--- Comment #1 from Jack Howarth <howarth.at.gcc at gmail dot com> ---
This Xcode 8 linker failure is suppressed when emacs 25.1 is built at -O0, but
occurs for -O1, -O2, -Os and -O3.