os: support runtime poller with os.File on Solaris

[ianlancetaylor]

The os test TestPipeThreads is failing on the Solaris builder, suggesting that for some reason os.File values are not working with the runtime poller. The code looks OK to me. I don't know why it is not working. Filing this issue to record the problem.

[gopherbot]

CL https://golang.org/cl/37092 mentions this issue.

[binarycrusader]

I haven't looked at the original change yet, but pipes are bi-directional on Solaris which tends to trip people up with things that "work" on Linux.

I don't know if this helps, but from pipe(2):

NOTES
Since a pipe is bi-directional, there are two separate flows of data.
Therefore, the size (st_size) returned by a call to fstat(2) with argu-
ment fildes[0] or fildes[1] is the number of bytes available for read-
ing from fildes[0] or fildes[1] respectively. Previously, the size
(st_size) returned by a call to fstat() with argument fildes[1] (the
write-end) was the number of bytes available for reading from fildes[0]
(the read-end).

When I get a moment, I'll see if I can figure something out.

[bradfitz]

Too late for Go 1.10 probably.