Further build profiling info

[Richard Purdie <richard.purdie@linuxfoundation.org>]

I'm sending these notes to the list since they might be useful to others
and it archives them.

Timing a build with license.bbclass:
consisting of 4847 tasks:

real 107m23.857s
user 376m31.640s
sys 46m51.020s

Without license.bbclass:
4409 tasks:

real 107m46.881s
user 369m6.670s
sys 46m19.890s

Without the setscene task and without license.bbclass:

3970 tasks:

real	105m36.940s
user	364m6.900s
sys	45m33.950s

which makes sense as setscene is a critical path dependency whilst the
license checks are not.

So a 120 second reduction for a drop of 439 tasks so a 0.27 second
overhead per task assuming they were all critical path. Numbers from the
graph suggested a 0.5 second task overhead so perhaps 50% were critical
path.

Interesting numbers and it suggests the situation isn't as bad as the
graph makes out though.

Cheers,

Richard