Some tips for debugging slow build times:
gn gen --tracelog trace.json to create a similar trace for
autoninja has logic for summarizing slow steps. Enable it via:
NINJA_SUMMARIZE_BUILD=1 autoninja -C out/Debug my_target
md5_check.py to optimize incremental builds.
PRINT_BUILD_EXPLANATIONS=1 to have these commands log which inputs changed.
ninja -n -d explain to figure out why ninja thinks a target is dirty.
restat=1 feature by not updating timestamps on outputs when their content does not change.