modern: bump base to Bionic

[ericLemanissier]

Until now, all modern images are based on Xenial, which is "End of standard support" since April 2021. It is a problem for projects like Qt which do not support Xenial any more. In the case of Qt, the compilation fails because xenial's system package for xcb-randr0 is too old (cf conan-io/conan-center-index#12620 (comment)). I don't think there is any acceptable workaround, cf conan-io/conan-center-index#12620 (comment))

CC @jgsogo @uilianries @danimtb @jcar87

Changelog: Fix : modern docker image are based on Ubuntu Bionic

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[uilianries]

My hand is shaking to merge it at once!

[uilianries]

It failed due a server error (not our side). Just restarted it now.

[ericLemanissier]

My hand shaking to merge it at once!

😄 Do we have a consensus that migrating to bionic is ok ?

[uilianries]

@ericLemanissier we still need some data, number of packages downloaded related to that distro.

Personally, I'm inclined to update it too.

[uilianries]

Archive:  ninja-linux.zip

  inflating: ninja                   

E: gnupg, gnupg2 and gnupg1 do not seem to be installed, but one of them is required for this operation

the clang-builder requires one of these packages

[uilianries]

We will discuss next week about this PR, hope we can update it soon.

[ericLemanissier]

for the record, all qt pull requests have been blocked by this issue for a month. As a consequence the last two versions of qt are not available on CCI. Some decision has to be taken one way or the other

[ericLemanissier]

@uilianries do we have a plan? Or should affected recipes raise ConanInvalidConfiguration based on lsb_release ?

[uilianries]

@ericLemanissier I built all images and I gonna test it today. Next week, if all occurs fine, we can start to migrate.

[uilianries]

I did some tests today and looks good.

I installed Boost, Poco, Cmake, opencv, ffmpeg and other pre-built packages from Conan Center, to a GCC 11 Ubuntu 18.04 from this PR and executed the test package, using option shared with libstdc++/11 combination. So far, no runtime errors.

[uilianries]

LGTM

[uilianries]

@ericLemanissier Thank you for updating it! This PR has been merged.