Fix debug logs showing up regardless of verbosity on macOS 12.7.1 / 13.6.3 / 14.2

[kit-ty-kate]

Fixes #48

This seems to be a bug in macOS 12.7.1 / 13.6.3 / 14.2, this has been reported to Apple.
This was tested successfully on Linux and macOS, i haven’t tried BSDs or Windows yet.

[kit-ty-kate]

Actually this seems to also happen on FreeBSD 13.1, i somehow never realized... This is embarassing.

@hannesm do you know if the debug logs were always there? They look like this:

$ opam install ...
[...]
Constructing initial basis...
Number of 0-1 knapsack inequalities = 2382
Constructing conflict graph...
Conflict graph has 774 + 104 = 878 vertices
[...]

[hannesm]

Dear @kit-ty-kate, yes I've seen this output since a long time. I don't remember whether it was always there or when it appeared. I don't find it too embarassing tbh, my brain is already used to not see it ;) [I wasn't aware this is only a thing on macOS and FreeBSD]

[kit-ty-kate]

Successfully tested on Linux, macOS, FreeBSD, OpenBSD, NetBSD, Windows/Cygwin, Windows/MinGW, Windows/MSVC (the last 3 using ocaml/opam#5769).

• no debug log is shown by default
• debug log is shown with --debug-level=2 or above