The goal here is to avoid potentially expensive fork()ing.
The time for a fork() is (for a process with no real heap usage
and thus few areas) 300-400us on my system. load_image() takes
3000us (3ms) or so, but this of course includes exec() time.
Overall, for compiling HaikuDepot (with a tweaked jam to use
posix_spawn on Haiku, not just on Linux) there is a slight
decrease in time:
before:
real 1m21.727s
user 1m2.131s
sys 0m43.029s
after:
real 1m19.472s
user 1m1.752s
sys 0m41.740s
Which is probably within the realm of "noise", so more benchmarks
are needed. Likely if we tweak our jam usage to not need as many
shells when running commands, this would be a much more noticeable
change.
Change-Id: I217f2476b1ed9aa18322b3c2bc8986571d89549a
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