Android : Android NDK: Warning: There are no modules to build in this project

I'm new in NDK development and I'm currently facing a problem, when I try to invoke the ndk build tool from cygwin terminal:

Android NDK: WARNING: There are no modules to build in this project!

I’m under windows (x64) and I use the r10d (64-bit) NDK. I try to invoke it from the root of my project that contains a jni folder with a simple .c file and an Android.mk:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

# Here we give our module name and source file(s)
LOCAL_MODULE    := mycfile
LOCAL_SRC_FILES := mycfile.c
APP_PLATFORM    := android-19

Thank you for your help !