Use -O not -O3: reduces ccan/tdb test time from 24 to 18 seconds.
[ccan] / ccan / container_of / test /
drwxr-xr-x   ..
-rw-r--r-- 356 compile_fail-bad-type.c
-rw-r--r-- 343 compile_fail-types.c
-rw-r--r-- 341 compile_fail-var-types.c
-rw-r--r-- 448 run.c