message: android-ndk-r21. before-deploy update
  before-deploy only cleans up if swig/bin folder exists, otherwise it ends up deleting all the files in the swig folder
diff: @@ -50,10 +50,10 @@ before_install:
  # android ndk: download and create toolchain
  - if [ $os_build == "android" ]; then
  - wget -nv -O android-ndk.zip https://dl.google.com/android/repository/android-ndk-r20b-linux-x86_64.zip;
  + wget -nv -O android-ndk.zip https://dl.google.com/android/repository/android-ndk-r21-linux-x86_64.zip;
  echo "Extracting NDK...wait";
  unzip -qq android-ndk.zip;
  - export NDK=$PWD/android-ndk-r20b;
  + export NDK=$PWD/android-ndk-r21;
  $NDK/build/tools/make_standalone_toolchain.py --arch $os_arch --api $android_api --stl libc++ --install-dir android-toolchain;
  export ANDROID_TOOLCHAIN=$PWD/android-toolchain;
  fi
  @@ -238,9 +238,11 @@ script:
  - cd ..
  before_deploy:
  - - cd swig/bin
  - - find . -type f | egrep -v '.*\.so$|.*\.dll$|.*\.dylib$|.*\.debug$' | xargs rm
  - - find . -empty -type d | xargs rm -r
  + - if [ -d swig/bin ]; then
  + cd swig/bin;
  + find . -type f | egrep -v '.*\.so$|.*\.dll$|.*\.dylib$|.*\.debug$' | xargs rm;
  + find . -empty -type d | xargs rm -r;
  + fi
  - cd ../..
  deploy:
  