pass branch name to docker build

docker/android-shstk/Dockerfile

@@ -1,4 +1,5 @@
 ARG DOCKER_PREFIX=wapmobil/
+ARG BRANCH=release
 FROM ${DOCKER_PREFIX}android
 
 ARG LIBS_BUILD_NUMBER=9999
@@ -10,7 +11,7 @@ ENV ANDROID_TOOLCHAIN=${ANDROID_NDK_HOME}/build/cmake/android.toolchain.cmake
 ENV NDK_PLATFORM="android-21"
 
 WORKDIR /soft
-RUN git clone -b release --single-branch --depth 1 --recursive https://git.shstk.ru/SHS/shstk.git
+RUN git clone -b ${BRANCH} --single-branch --depth 1 --recursive https://git.shstk.ru/SHS/shstk.git
 
 WORKDIR /soft/shstk_build_host
 RUN cmake -G Ninja -DICU=0 -DCROSSTOOLS=1 -DBUILD_NUMBER=${LIBS_BUILD_NUMBER} ../shstk \