Get and extract NDK

Author: ErjanGavalji

.travis.yml

@@ -6,6 +6,12 @@ git:
 before_install:
     - sed -i 's/git@github.com:/https:\/\/github.com\//' .gitmodules
     - git submodule update --init --recursive
+    - wget http://dl.google.com/android/ndk/android-ndk-$NDK_VERSION-linux-x86_64.bin
+    - chmod +x android-ndk-$NDK_VERSION-linux-x86_64.bin
+    - ./android-ndk-$NDK_VERSION-linux-x86_64.bin | egrep -v ^Extracting
+    - export ANDROID_NDK_HOME=`pwd`/android-ndk-$NDK_VERSION
+    - export PATH=${PATH}:${ANDROID_NDK_HOME}
+
 android:
     components:
         - platform-tools