[PATCH] PR85678: Change default to -fno-common

[David Edelsohn]

>> Has this been bootstrapped and regression tested?
>
> Yes, it bootstraps OK of course. I ran regression over the weekend, there
> are a few minor regressions in lto due to relying on tentative definitions
> and a few latent bugs. I'd expect there will be a few similar failures on
> other targets but nothing major since few testcases rely on -fcommon.

This almost certainly will break AIX.

- David