This way, warnings from headers that come from another package (in
particular linux-headers) won't show up when they get included.
To make sure we still track dependencies, use -MD instead of -MMD.
Since ninja 1.8.0[0] and samurai 0.2[1], output mtime is always
recorded after a job succeeds, and outputs are considered dirty if
the recorded mtime is older than any input. This means that even
if a command partially writes its output then fails (for example,
if run with stdout redirected to a file), it will still get re-run
during the next build.
This means that outputs no longer have to be written atomically
(i.e. renamed into place) in order to ensure a correct build, and
we can drop the idiom `command >$out.tmp && mv $out.tmp $out`.
[0] https://github.com/ninja-build/ninja/commit/04d886b11041bb59d01df794cce7a1e8cad2250d
[1] https://github.com/michaelforney/samurai/commit/799bc5a4719b90a1026c129b55b92c0bccf97eeb
Michael Forney