Makefile: do not set NEEDS_LIBICONV for Solaris 8

This breaks my build on Solaris 8, as there is no separate libiconv. The history of this line is somewhat convoluted. In 2fd955c (in November 2005), NEEDS_LIBICONV was turned on for all Solaris builds, claiming to "fix an error in Solaris 10 by setting NEEDS_LIBICONV". Later, e15f545 (in February of 2006) claimed that "Solaris 9+ don't need iconv", and moved NEEDS_LIBICONV into a section for Solaris 8. Furthermore, Brandon Casey claims in <5A1KxlhmUIHe8iXPxnXYuNXsq0Yjlbwkz2eBin3z7ELuL9nK-4tSpw@cipher.nrlssc.navy.mil> that he does not set NEEDS_LIBICONV for Solaris 7. So either one of those commits is totally wrong, or there is some other magic going on where some Solaris installs need it and others don't. Given Brandon's statement and my problems on Solaris 8 with NEEDS_LIBICONV, I am inclined to think the first commit was bogus, and that NEEDS_LIBICONV shouldn't be set for Solaris at all by default. If somebody wants to use iconv and has installed it manually, they can set it in their config.mak. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Shawn O. Pearce <spearce@spearce.org>