cc/gcc: do not build manuals in parallel

Reported-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Reported-by: Johannes Stezenbach <js@sig21.net>
Tested-by: Johannes Stezenbach <js@sig21.net>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
(transplanted from c800b7d6a50c267c3e0a64829da4b082e260deff)

#!/bin/sh

call_to=@@DEFAULT_LD@@

case "${CTNG_LD_IS}" in

    bfd)    call_to=bfd;;

    gold)   call_to=gold;;

esac

exec "${0}.${call_to}" "$@"

exit $?