🐛 Redirect stdout to devnull during precompilation

Calling `redirect_stdout` without any arguments redirects the output to
a newly created `Pipe`[^1] (which is mostly a wrapper around standard
*nix pipes). Not reading data from this `Pipe` can result in
precompilation to hang, e.g. in CI environments such as GitHub Actions
or as reported here[^2].

This is due to a fundamental expectation that a (*nix) kernel has on
pipes, as documented[^3] "write will block until sufficient data has
been read from the pipe to allow the write to complete". For this reason
never reading from `new_stdout` may cause the precompilation to hang.
Explicitly redirecting to `devnull` circumvents this expectation and
ensures precompilation succeeds.

[^1]: https://github.com/JuliaLang/julia/blob/9233a16172139c06107b475480bfce098f10a8a6/base/stream.jl#L1259
[^2]: https://discourse.julialang.org/t/when-i-add-any-package-prettytables-will-get-stuck-here-and-cannot-be-executed-i-need-to-control-c-to-close-it
[^3]: https://man7.org/linux/man-pages/man7/pipe.7.html

src/precompilation.jl

@@ -68,7 +68,7 @@ PrecompileTools.@setup_workload begin
     # We will redirect the `stdout` and `stdin` so that we can execute the pager and input
     # some commands without making visible changes to the user.
     old_stdout = Base.stdout
-    new_stdout = redirect_stdout()
+    new_stdout = redirect_stdout(devnull)
 
     # In HTML, we use `display` if we are rendering to `stdout`. However, even if we are
     # redirecting it, the text is still begin shown in the display. Thus, we create a buffer