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

libgloss/riscv/sys_getcwd.c

@@ -0,0 +1,9 @@
+#include <machine/syscall.h>
+#include <sys/types.h>
+
+/* Stub.  */
+char *
+_getcwd(char *buf, size_t size)
+{
+  return NULL;
+}