Use -O not -O3: reduces ccan/tdb test time from 24 to 18 seconds.
[ccan] / ccan / antithread / test /
drwxr-xr-x   ..
-rw-r--r-- 1037 run-lock.c
-rw-r--r-- 628 run-simple.c
-rw-r--r-- 570 run-spawn-NULL.c
-rw-r--r-- 917 run-spawn.c
-rw-r--r-- 500 run-tell.c
-rw-r--r-- 656 run-tell_parent.c