all: fix adjustment of /proc/$pid/cmdline by single binary

all: fix adjustment of /proc/$pid/cmdline by single binary

When configured with --enable-single-binary tools issue incorrect prctl:

  prctl(PR_SET_KEEPCAPS, ...)      = -1 EINVAL (Invalid argument)

PR_SET_MM_ARG_START is not a prctl 'option' parameter, it's 'arg2'
parameter for the option PR_SET_MM.  It also has to have 'arg4' and
'arg5' set to 0 explicitly, otherwise the kernel also returns -EINVAL.

* src/coreutils.c (launch_program): Fix prctl arguments.
* NEWS: Mention the improvement.
Fixes https://bugs.gnu.org/52800