Check for ld --hash-style flag fails for oldconfig target

[Will Newton]

Hi all,

The check for whether ld supports the --hash-style option in Rules.mak
fails when building the oldconfig target in buildroot. One potential
fix for this might be to add another check for this target like the
one for install_headers, but I think it's quite a fragile approach -
there may be other targets that are similarly affected.

Would it be possible just to remove that check? The user will get a
warning a little later when they try and link.