coverage targets ?

I'm trying to close the issue #2805, and i'm discovering something strange:

• ninja coverage -> call meson --internal
• ninja coverage-html -> call lcov
• ninja meson-coverage -> call meson --internal (coverage alias)
• ninja meson-coverage-html -> call lcov (coverage-html alias)

The calls to lcov are currently implemented twice, in scripts/coverage.py and backends/ninjabackend.py. And the implementations are not the same…

That should be cleaned. One solution is to write only ninja targets:

• coverage-html : call lcov, genhtml (just like in scripts/coverage.py)
• coverage-txt : call gcovr
• coverage-xml : call gcovr
• coverage : depends on the 3 other targets.

EDIT : I'm seeing that the move went from ninja targets to meson internal script. Is there a reason ? Anyway, one would suppose meson-* targets will call meson --internal, and that's not the case.