Respect db_home setting even for the SYSTEM account

We should not blindly set the home directory of the SYSTEM account to
/home/SYSTEM, especially not when that value disagrees with what is
configured via the `db_home` line in the `/etc/nsswitch.conf` file.

This fixes git-for-windows/git#435

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

winsup/cygwin/uinfo.cc

@@ -2307,7 +2307,11 @@ pwdgrp::fetch_account_from_windows (fetch_user_arg_t &arg, cyg_ldap *pldap)
 	 it to a well-known group here. */
       if (acc_type == SidTypeUser
 	  && (sid_sub_auth_count (sid) <= 3 || sid_id_auth (sid) == 11))
-	acc_type = SidTypeWellKnownGroup;
+	{
+	  acc_type = SidTypeWellKnownGroup;
+	  home = cygheap->pg.get_home (pldap, sid, dom, domain, name,
+				       fully_qualified_name);
+	}
       switch ((int) acc_type)
 	{
 	case SidTypeUser: