user: implement mlibc as the libc, finally.

It's finally done..

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

user/include/mlibc/options/glibc/generic/glibc-signal.cpp

@@ -0,0 +1,14 @@
+#include <errno.h>
+#include <signal.h>
+#include <bits/ensure.h>
+#include <mlibc/debug.hpp>
+#include <mlibc/glibc-sysdeps.hpp>
+
+int tgkill(int tgid, int tid, int sig) {
+	MLIBC_CHECK_OR_ENOSYS(mlibc::sys_tgkill, -1);
+	if(int e = mlibc::sys_tgkill(tgid, tid, sig); e) {
+		errno = e;
+		return -1;
+	}
+	return 0;
+}