cmd/go: add AIX support
cmd/go: add AIX support

For gccgo code avoid --whole-archive and -(.  Use -blibpath instead of
-rpath.

Change-Id: Ieb55292866d56097db1997cd721f1bc861cdbd6a
Reviewed-on: https://go-review.googlesource.com/86956
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

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