add method to find the android ndk build executable in a common way for all sub projects that need to build a native android lib

build.gradle

@@ -96,6 +96,26 @@ task wrapper(type: Wrapper, description: 'Creates and deploys the Gradle wrapper
     gradleVersion = '1.11'
 }
 
+String findNDK() {
+    def ndkBuildFile = "ndk-build"
+    // if windows, use ndk-build.cmd instead
+    if (System.properties['os.name'].toLowerCase().contains('windows')) {
+        ndkBuildFile = "ndk-build.cmd"
+    }
+
+    // ndkPath is defined in the root project gradle.properties file
+    String ndkBuildPath = ndkPath + File.separator + ndkBuildFile
+    //Use the environment variable for the NDK location if defined
+    if (System.env.ANDROID_NDK != null) {
+        ndkBuildPath = System.env.ANDROID_NDK + File.separator + ndkBuildFile
+    }
+    if (new File(ndkBuildPath).exists()) {
+        return ndkBuildPath
+    } else {
+        return null
+    }
+}
+
 //class IncrementalReverseTask extends DefaultTask {
 //    @InputDirectory
 //    def File inputDir