The Solaris assembler uses a different syntax for section directives.

Fixes https://gcc.gnu.org/PR85429.

Change-Id: I1e54dffee3290046dbb68ba4e90ab795c6b72571
Reviewed-on: https://go-review.googlesource.com/109140
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>