s3:configure: add support for Solaris' ld -z ignore

try linker flags for ignoring unused libs in this order:
-Wl,--as-needed (gcc like + binutils)
-Wl,-z,ignore (gcc like + Solaris linker)
-z ignore (old Sun C)

source3/configure.in

@@ -1758,22 +1758,18 @@ fi
 
 AC_MSG_RESULT($BLDSHARED)
 
-if test x"${ac_cv_prog_gnu_ld}" = x"yes"; then
+for flags in "-Wl,--as-needed" "-Wl,-z,ignore" "-z ignore" ; do
 	saved_ldflags="$LDFLAGS"
-	AC_MSG_CHECKING([if --as-needed works])
-	LDFLAGS="--as-needed $saved_ldflags"
+	AC_MSG_CHECKING([if $flags works])
+	LDFLAGS="$flags $saved_ldflags"
 	AC_TRY_LINK([],[],
 		[AC_MSG_RESULT([yes])
-		LD_AS_NEEDED_FLAG=--as-needed],
-		AC_MSG_RESULT([no]))
-	AC_MSG_CHECKING([if -Wl,--as-needed works])
-	LDFLAGS="-Wl,--as-needed $saved_ldflags"
-	AC_TRY_LINK([],[],
-		[AC_MSG_RESULT([yes])
-		LD_AS_NEEDED_FLAG=-Wl,--as-needed],
+		LD_AS_NEEDED_FLAG=$flags
+		ld_as_needed_flag_found=yes],
 		AC_MSG_RESULT([no]))
 	LDFLAGS="$LD_AS_NEEDED_FLAG $saved_ldflags"
-fi
+	test x"$ld_as_needed_flag_found" = xyes && break
+done
 
 # for historical reasons almost all linkers don't complain about unresolved
 # symbols in shared libs. Except for the internal samba modules we want to get