I am following this tutorial on how to use NDK with Android Studio: http://www.ph0b.com/android-studio-gradle-and-ndk-integration/
I have android studio 0.9.3 insta
Try add the full path name both with android-support-v7-appcompat.jar and android-support-v4.jar files after android.jar,
For example
D:\ANDROID\workspace\NDKSample\app\src\main>javah -d jni -classpath D:\ANDROID\kits\sdk\platforms\android-19\android.jar;D:\ANDROID\kits\sdk\extras\android\support\v7\appcompat\libs\android-support-v7-appcompat.jar;D:\ANDROID\kits\sdk\extras\android\support\v7\appcompat\libs\android-support-v4.jar;D:\ANDROID\workspace\NDKSample\app\build\intermediates\classes\debug com.jihv.gildas.ndksample.MainActivity