Expect support schedule jobs dynamically according to current available memory resource

[CHEN Feng]

For a large project, many times, the build failure is often due to oom, so don't start new jobs when the available memory resource is low is a feasible way to relieve this problem.

But ninja does not response this feature request many times, see 1571, and 1441.

So I strongly expect samurai can support this feature. Many thanks!