Ensure rebuildability from source of all provided packages over the lifecycle of the product

[dirkmueller]

For certain products, like the SLE family of products (as an example) we'd like to ensure that at any point in time, given the latest state of released updates, provided "src.rpms" and in extension sources are rebuildable as a user. That means if an update (could be security or maintenance update on existing SPs or newly scheduled feature/version update on newer SP) causes other already provided distribution packages to be no longer buildable from source, it should be caught, reported and ideally mitigated as part of the introduction of the update.

There is also a supportability use case in there: if users can not rebuild from source, also we likely can no longer do so, which means if there is any desire to update the package (to add a security or a bug fix, for example) we first spend unplanned time on fixing the build regression. discovering those issues earlier would be beneficial to disentangle the workload.

[coolo]

First step: creating bug reports for sources on SP4 medium not compiling on SP4: https://bugzilla.suse.com/buglist.cgi?quicksearch=FTBFS%20SP4

[coolo]

Ok, bugs against failing packages are too easy to kill by packagers with "not my fault"

[bmwiedemann]

As an extra data point, http://rb.zq1.de/sle/15.4/reproducible-frontrunner-20220326.json has 173 FTBFS entries. That includes non-SLE packages and failures from building with -j1 in 2037.