[Bug boehm-gc/66848] boehm-gc fails test suite on x86_64-apple-darwin15

[howarth.at.gcc at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66848

--- Comment #8 from Jack Howarth <howarth.at.gcc at gmail dot com> ---
Note that radr://21372179 has been closed by Apple as "behaves as expected' so
that they believe the bug lies in the FSF gcc boehm-gc code.