RISC-V: Moved syscalls to separate files to fix aliasing problems.

libgloss/riscv/sys_exit.c

@@ -0,0 +1,10 @@
+#include <machine/syscall.h>
+#include "internal_syscall.h"
+
+/* Exit a program without cleaning up files.  */
+void
+_exit(int exit_status)
+{
+  syscall_errno (SYS_exit, exit_status, 0, 0, 0, 0, 0);
+  while (1);
+}