waf:lib/replace fix iconv checks on HP/UX

waf:lib/replace fix iconv checks on HP/UX

we need to copy away the list of LDFLAGS
to be tried before modifying it instead of
just creating a new reference and then continuing
with a modified list while it should have been
reset back to the original value

Bug: https://bugzilla.samba.org/show_bug.cgi?id=9911

Signed-off-by: Christian Ambach <ambi@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Thu Feb 13 02:01:03 CET 2014 on sn-devel-104