fix ios build

[trittsv]

This PR fixes iOS builds.

On iOS it takes special care to build a executable, app bundle identifier are needed etc.

In a typical iOS build you only want to have the kvazaar lib to link with your app.

Because of that the option -DBUILD_KVAZAAR_BINARY=OFF is introduced to be able to build for iOS.

The build error looked like this:

cmake -G Xcode \
  -DBUILD_SHARED_LIBS=OFF \
  -DCMAKE_TOOLCHAIN_FILE=./ios.toolchain.cmake \
  -DPLATFORM=OS64 \
  -DBUILD_TESTS=OFF \
  -DCMAKE_BUILD_TYPE=Release \
  .. \
  && \
  xcodebuild -project kvazaar.xcodeproj \
                        -scheme install \
                        -configuration Release \
                        -quiet \
                        -allowProvisioningUpdates \
                        -destination generic/platform=iOS \
                        -derivedDataPath ./build \
                        build
. . .
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/sventrittler/workspace/thridparty/kvazaar/x
note: Run script build phase 'Generate CMakeFiles/ZERO_CHECK' will be run during every build because the option to run the script phase "Based on dependency analysis" is unchecked. (in target 'ZERO_CHECK' from project 'kvazaar')
/Users/sventrittler/workspace/thridparty/kvazaar/x/kvazaar.xcodeproj: error: Bundle identifier is missing. kvazaar-bin doesn't have a bundle identifier. Add a value for PRODUCT_BUNDLE_IDENTIFIER in the build settings editor. (in target 'kvazaar-bin' from project 'kvazaar')
** BUILD FAILED **

[fador]

Thanks!