Use "--config-cache" configure option to speed up builds
A lot of time is spent in ./configure rather than actual builds, which hurts build test performance.
One option would be to to have a persistent directory on each slave where we keep config.cache files for all the various projects. The call would then look like:
./configure --config-cache --cache-file=/foo/bar/`basename $PWD`/config.cache
at which point we can expect at least a 50% reduction (probably more on loaded systems) in ./configure time. One could include $JOB_NAME into the --cache-file path to be safe?
Good idea! I asked Paolo Bonzini for some help but I found a link to https://gitlab.com/gnuwget/wget2/wikis/Developer-hints:-Increasing-speed-of-GNU-toolchain#cccflags-dependent-usage-of-configure-caching in a mailing list (I don't think it is public) I am subscribed to.
Not sure if we would already win just caching system wide settings?