PSA: CI compile flags edition

[Alexandros Frantzis]

On Wed, Mar 02, 2016 at 07:58:44PM +0200, Alexandros Frantzis wrote:
> On Tue, Mar 01, 2016 at 05:08:47PM +1100, raof at ubuntu.com wrote:
> > Hey all,
> > 
> > Pursuant to Alan's comment¹ and subsequent follow-ons, in the interests of
> > rapid CI turnaround Jenkins now does regular CI runs with
> > DEB_BUILD_OPTIONS=noopt. This currently means it does an -O0 build, and will
> > disable LTO when that lands.
> > 
> > These changes don't apply to the pre-autolanding builds; they will continue
> > to be run with the standard Debian optimisations (-O2) and with LTO (again,
> > once that lands).
> > 
> > For those playing at home, the relevant parameter is $run_landing_checks on
> > build-2-binpkg-mir if you've got any other checks that should be enabled
> > prior to landing but not every CI run.
> > 
> > ¹: https://code.launchpad.net/~raof/mir/fix-and-enable-lto/+merge/282133/comments/733096
> 
> Thanks Chris!
> 
> I noticed that after the LTO branch landed, the mir-ci jobs started
> taking longer, which is not consistent with disabling optimizations and
> LTO.
> 
> It turned out there was a misconfiguration in the build-mir job, causing
> $run_landing_checks to always be true in all invocations of
> build-2-binpkg-mir. I corrected the problem and it had the effect we
> want on non-cross builds (e.g., see [1] vs [2]).
> 
> Unfortunately, the problem persists on cross builds (e.g., see [3]), due
> to an sbuild peculiarity/bug: when cross building, sbuild overwrites
> DEB_BUILD_OPTIONS (setting it to "nocheck"). See the the debian bug
> report [4] for more info.
> 
> I will investigate a few potential workarounds tomorrow (unless someone
> else gets to it first).
> 

Cross building is now fixed (see [1]) using a workaround in ~/.sbuildrc.
I have also added the fix to the preparation jobs, so it will be applied
automatically if we need to redeploy.

[1] https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/313/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/consoleFull