runtime2: don't check fcntl errno in checkfds on AIX and Solaris
On AIX and Solaris the errno value is fetched using m.mOS.perrno.
When checkfds is called, that value has not yet been set up by minit.
Since the error value doesn't really matter in checkfds,
don't bother to check it on AIX and Solaris.
Fixes #61584
Change-Id: I4e679ee3fdad4f0b833ae102597b2d6b8cb46cb6
Reviewed-on: https://go-review.googlesource.com/c/go/+/513215
Run-TryBot: Ian Lance Taylor <iant@golang.org> Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com> Reviewed-by: Roland Shoemaker <roland@golang.org>
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