code: do not store messages on stack

This is to prevent stack overflows if messages are big.
Partial revert of 0c6d1256
2 jobs for master in 1 minute and 1 second (queued for 6 seconds)
Status Name Job ID Coverage
failed build_test_nix #1436418


skipped sonar_static_analysis #1436422
Name Stage Failure
build_test_nix Build
error: anonymous function at /nix/store/fa7d7b3920mzvbk9ad2nv14gp6n4xpvl-source/pkgs/development/tools/build-managers/meson/default.nix:1:1 called with unexpected argument 'stdenv', at /nix/store/fa7d7b3920mzvbk9ad2nv14gp6n4xpvl-source/lib/customisation.nix:69:16
(use '--show-trace' to show detailed location information)

NoInput "You need to specify store paths either as stdin or as a cli argument"
Uploading artifacts for failed job
Uploading artifacts...
WARNING: /builds/simgrid/remote-simgrid/gcov-txt: no matching files
ERROR: No files to upload
Cleaning up file based variables
ERROR: Job failed: exit code 1