Use -O not -O3: reduces ccan/tdb test time from 24 to 18 seconds.
[ccan] / ccan / typesafe_cb /
drwxr-xr-x   ..
-rw-r--r-- 2069 _info
drwxr-xr-x - test
-rw-r--r-- 4523 typesafe_cb.h