v0.4.2b: provided a gradle build task for FroyoGLES20Fix

SPD-classes/build.gradle

@@ -3,4 +3,25 @@ apply plugin: 'com.android.library'
 android {
     compileSdkVersion 23
     buildToolsVersion "24.0.2"
+
+    task ndkBuild(type: Exec){
+        description "builds JNI libs from source. " +
+                "This requires the Android NDK and is optional as precompiled libs are provided."
+
+        workingDir = "./src/main"
+        def ndkDir = android.ndkDirectory
+
+        //Need to start cmd first on windows systems, otherwise these are the same
+        if (System.properties["os.name"].toLowerCase().contains("windows")){
+            commandLine "cmd", "/c" , "$ndkDir${File.separator}ndk-build " +
+                    "NDK_APPLICATION_MK=./jniSources/Application.mk " +
+                    "NDK_LIBS_OUT=./jniLibs"
+        } else {
+            commandLine "$ndkDir${File.separator}ndk-build " +
+                    "NDK_APPLICATION_MK=./jniSources/Application.mk " +
+                    "NDK_LIBS_OUT=./jniLibs"
+        }
+
+    }
+
 }

SPD-classes/src/main/jniSources/Application.mk

@@ -0,0 +1,3 @@
+APP_ABI := armeabi x86
+APP_BUILD_SCRIPT := ./jniSources/Android.mk
+APP_OPTIM := release

SPD-classes/src/main/jniSources/README.txt

@@ -7,6 +7,5 @@ building from source can still do so.
 
 There is no functional difference between using the provided .so files, and compiling your own.
 
-In order to compile these files you will need the Android NDK.
-
-TODO: provide build instructions, or a build script, or make a gradle task.
+These sources can be compiled through the gradle task SPD-classes:ndkBuild on a system with the
+Android NDK installed and configured.