Ninja, Icecream, ccache (I personally don't use that one), LLD or mold, breaking up the largest compilation units, avoiding internal static libraries at least f

Ninja, Icecream, ccache (I personally don't use that one), LLD or mold, breaking up the largest compilation units, avoiding internal static libraries at least for debug builds, not choosing the maximum amount of debug info... can result in edit-compile-run cycles under five seconds. Time for clean builds strongly depends on project size and template usage, obviously.