Bug#755061: GCC 4.9 produces a bad binary on arm64

[Wookey <wookey@wookware.org>]

Package: gcc-4.9
Followup-For: Bug #755061

A bit more investigation found that the issue could not be reproduced
building with the ubuntu (trusty) toolchain on trusty. And even more
interestingly that if the working (on trusty) binary of gpg-agent was
copied to a debian system, it still failed in the same way, which
suggests that something odd is going on and that the problem is
actually something in the Debian environment, and maybe not gpg-agent
itself at all, possibly one of the libraries used by the
package. Although it's very odd that optimisation levels affect this.

So right now it's not at all clear which package/binary is actually at
fault. Needs more investigation.

Wookey