buildroot

binutils: ensure TARGET_CONFIGURE_ARGS is taken into consideration for subdirs

Binutils runs the configure scripts of subdirs at make time, so we need a
custom build command to ensure TARGET_CONFIGURE_ARGS are taken into
consideration for those (E.G. for musl gettext handling).

Reported-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>