Only Glibc on Linux has execinfo.h
Only Glibc on Linux has execinfo.h

Fix as done elsewhere so that it builds correctly on Musl libc
as well as Glibc.

Signed-off-by: Justin Cormack <0ce7911e6479995d6c346d6f03eb723b5135309e@specialbusservice.com>

mologie/capnproto,pjulien/capnproto,pjulien/capnproto,mologie/capnproto,mologie/capnproto,pjulien/capnproto