[Bug driver/66293] Support -Weverything to enable all warnings

[jeanmichael.celerier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66293

--- Comment #5 from Jean-Michaël Celerier <jeanmichael.celerier at gmail dot com> ---
> In my experience, options like -Weverything tend to be too noisy to be generally useful for projects of non-trivial size.

It's always possible to run -Weverything -Wno-foo -Wno-bar to remove unwanted
warnings. It's a bit more work upfront, but will bring benefits at each
compiler update. Generally speaking, I'd say that there are more "useful" than
"useless" warnings, hence it's less work to disable the useless ones, than to
enable the useful ones.