message: [build] make dbus user and group configurable in Android.mk
  This allow users to override the dbus user and group with non-root
  configuration.
diff: @@ -147,10 +147,13 @@ LOCAL_MODULE_CLASS := ETC
  LOCAL_MODULE := otbr-agent.conf
  LOCAL_MODULE_TAGS := eng
  +OTBR_AGENT_USER ?= root
  +OTBR_AGENT_GROUP ?= root
  +
  LOCAL_MODULE_PATH := $(TARGET_OUT_ETC)/dbus-1/system.d
  LOCAL_SRC_FILES := src/agent/otbr-agent.conf
  $(LOCAL_PATH)/src/agent/otbr-agent.conf: $(LOCAL_PATH)/src/agent/otbr-agent.conf.in
  - sed -e 's/@OTBR_AGENT_USER@/root/g' -e 's/@OTBR_AGENT_GROUP@/root/g' $< > $@
  + sed -e 's/@OTBR_AGENT_USER@/$(OTBR_AGENT_USER)/g' -e 's/@OTBR_AGENT_GROUP@/$(OTBR_AGENT_GROUP)/g' $< > $@
  include $(BUILD_PREBUILT)
  endif # ifeq ($(OTBR_ENABLE_ANDROID_MK),1)
  