Code review comment for lp:~thomas-voss/mir/explicit-gcc-version

We've talked about this extensively between Thomas and the Foundations
team (which owns the toolchain). Most of the archive is fine, including
most C++ projects, since libstdc++ in general offers a stable ABI except
when explicitly stated upstream; when we receive such statements from
upstream we deal with that differently, but that's not a problem at the
moment.

The specific problem at issue is that C++11 is experimental at the
toolchain level, and it isn't guaranteed that g++/libstdc++ will
preserve ABI stability there. We therefore need to make sure the
(small) set of packages using it are migrated together; this does *not*
need to be done in sync with the change of our default gcc/g++ version,
and in fact it's much easier to coordinate if it's decoupled. This is
why Thomas is working on all our C++11 packages to make all of them use
a specific version of g++, so that they can deal with orderly
transitions to new g++ versions on their own schedule with SONAME
changes etc. as required. This MP is one of many such.

For more details, please see:

  https://wiki.ubuntu.com/cpp-11