s3:Makefile: make DSO_EXPORTS_CMD more portable (#8531)

s3:Makefile: make DSO_EXPORTS_CMD more portable (#8531)

It sems like every not completely trivial sed expression should be tested with
Solaris' sed.  Its regexp engine is way more limited than the one of GNU
sed. Thanks to Michael Pelletier for finding this! This fixes bug #8531

Autobuild-User: Björn Jacke <bj@sernet.de>
Autobuild-Date: Thu Oct 20 23:15:05 CEST 2011 on sn-devel-104
(cherry picked from commit 37be1df3d7534c2cc8e1e25614164c2178372b94)
(cherry picked from commit 763ad499aa4423c5e68a75f20f2ba8ee967e5984)
(cherry picked from commit 53b551d160a9e5b645aaa6582d7ffc82e5e52b59)