Makefile: remove pointless conditional assignment in SunOS section

It is true that NEEDS_RESOLV is needed on SunOS if NO_IPV6 is set since hstrerror() resides in libresolv, but performing this test at its current location is not very useful. It will only have any effect if the user modifies the make variables from the make command line, and will have no effect if a config.mak file is used. A better location for this conditional would have been further down in the Makefile after the config.mak and config.mak.autogen had been parsed. Rather than adding clutter to the Makefile for a conditional that will likely never be triggered, just remove it, and any user on SunOS that manually sets NO_IPV6 can also set NEEDS_RESOLV. Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil> Signed-off-by: Junio C Hamano <gitster@pobox.com>