kbuild: rename ld-option to cc-ldoption

ld-option is misnamed as it test options to gcc, not to ld.
Renamed it to reflect this.

Cc: Andi Kleen <andi@firstfloor.org>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>