user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/options/linux/generic/sys-prctl.cpp

@@ -0,0 +1,25 @@
+
+#include <stdarg.h>
+#include <errno.h>
+#include <bits/ensure.h>
+#include <sys/prctl.h>
+
+#include <mlibc/debug.hpp>
+
+#include "mlibc/linux-sysdeps.hpp"
+
+int prctl(int op, ...) {
+	MLIBC_CHECK_OR_ENOSYS(mlibc::sys_prctl, -1);
+
+	int val;
+	va_list ap;
+	va_start(ap, op);
+	if(int e = mlibc::sys_prctl(op, ap, &val); e) {
+		errno = e;
+		return -1;
+	}
+	va_end(ap);
+
+	return val;
+}
+