sys/fuchsia: add the mtrace system call

[noncombatant]

[codecov[bot]]

Codecov Report

Merging #3297 (d7d17d8) into master (c2a623d) will increase coverage by 0.0%. The diff coverage is n/a.

Impacted Files	Coverage Δ
prog/hints.go	86.5% <0.0%> (-2.6%)	:arrow_down:
prog/any.go	85.2% <0.0%> (-2.0%)	:arrow_down:
prog/size.go	90.5% <0.0%> (-1.9%)	:arrow_down:
prog/mutation.go	88.8% <0.0%> (-0.8%)	:arrow_down:
prog/prog.go	82.3% <0.0%> (-0.8%)	:arrow_down:
pkg/csource/csource.go	78.1% <0.0%> (+0.2%)	:arrow_up:
prog/target.go	57.1% <0.0%> (+0.5%)	:arrow_up:
prog/rand.go	92.7% <0.0%> (+0.6%)	:arrow_up:
prog/minimization.go	91.1% <0.0%> (+0.8%)	:arrow_up:
sys/linux/init.go	60.8% <0.0%> (+1.5%)	:arrow_up:
... and 1 more

[noncombatant]

Landing this one first will minimally allow us to use zx_resource in other PRs.

I don't know what the race test failure means. Clues?

[dvyukov]

I don't know what the race test failure means. Clues?

This is an unrelated flake. I've sent #3305 to fix it. Also restarted CI on this PR.