os: pass -s to hostname on AIX
os: pass -s to hostname on AIX

Change-Id: I4380850d50b33a34561d4e4bfa704abd2ab62516
Reviewed-on: https://go-review.googlesource.com/79375
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

golang/gofrontend,golang/gofrontend,golang/gofrontend,golang/gofrontend