Fixed the build break of helix/rev1:OLED_sample caused by PR #4462.

keyboards/helix/rev1/keymaps/OLED_sample/rules.mk

@@ -0,0 +1,20 @@
+# Build Options
+#   change to "no" to disable the options, or define them in the Makefile in
+#   the appropriate keymap folder that will get included automatically
+#
+BOOTMAGIC_ENABLE = no       # Virtual DIP switch configuration(+1000)
+MOUSEKEY_ENABLE = no       # Mouse keys(+4700)
+EXTRAKEY_ENABLE = yes       # Audio control and System control(+450)
+CONSOLE_ENABLE = no         # Console for debug(+400)
+COMMAND_ENABLE = no        # Commands for debug and configuration
+NKRO_ENABLE = yes            # Nkey Rollover - if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
+BACKLIGHT_ENABLE = no      # Enable keyboard backlight functionality
+MIDI_ENABLE = no            # MIDI controls
+AUDIO_ENABLE = no           # Audio output on port C6
+UNICODE_ENABLE = no         # Unicode
+BLUETOOTH_ENABLE = no       # Enable Bluetooth with the Adafruit EZ-Key HID
+RGBLIGHT_ENABLE = yes        # Enable WS2812 RGB underlight.
+SWAP_HANDS_ENABLE = no        # Enable one-hand typing
+
+# Do not enable SLEEP_LED_ENABLE. it uses the same timer as BACKLIGHT_ENABLE
+SLEEP_LED_ENABLE = no    # Breathing sleep LED during USB suspend