PSA: CI compile flags edition

[Alexandros Frantzis]

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).

[1] https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/306/arch=amd64,compiler=gcc,platform=mesa,release=xenial/consoleFull
[2] https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/307/arch=amd64,compiler=gcc,platform=mesa,release=xenial/consoleFull
[3] https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/307/arch=cross-armhf,compiler=gcc,platform=android,release=vivid+overlay/consoleFull
[4] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=775539