linux-user: remove host stime() syscall

linux-user: remove host stime() syscall

stime() has been withdrawn from glibc
(12cbde1dae6f "Use clock_settime to implement stime; withdraw stime.")

Implement the target stime() syscall using host
clock_settime(CLOCK_REALTIME, ...) as it is done internally in glibc.

Tested qemu-ppc/x86_64 with:

	#include <time.h>
	#include <stdio.h>

	int main(void)
	{
		time_t t;
		int ret;

		/* date -u -d"2019-11-12T15:11:00" "+%s" */
		t = 1573571460;
		ret = stime(&t);
		printf("ret %d\n", ret);
		return 0;
	}

        # date; ./stime; date
        Tue Nov 12 14:18:32 UTC 2019
        ret 0
        Tue Nov 12 15:11:00 UTC 2019

Buglink: https://bugs.launchpad.net/qemu/+bug/1852115
Reported-by: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20191112142556.6335-1-laurent@vivier.eu>