[libc] Setup hdrgen for ioctl

This patch adds some hdrgen yaml for ioctl(). Otherwise the function
never actually ends up being available in a full build. This is the last
thing that is needed to enable turning on LIBCXX_ENABLE_RANDOM_DEVICE.

Author: boomanaiden154

libc/include/sys/ioctl.yaml

@@ -5,4 +5,10 @@ macros: []
 types: []
 enums: []
 objects: []
-functions: []
+functions:
+  - name: ioctl
+    return_type: int
+    arguments:
+      - type: int
+      - type: unsigned long
+      - type: '...'