ccache android builds in ci

contrib/ci/docker/android.dockerfile

@@ -4,4 +4,4 @@ RUN /bin/bash -c 'sed -i "s/main/main contrib/g" /etc/apt/sources.list'
 RUN /bin/bash -c 'apt-get -o=Dpkg::Use-Pty=0 -q update && apt-get -o=Dpkg::Use-Pty=0 -q dist-upgrade -y && apt-get -o=Dpkg::Use-Pty=0 -q install -y android-sdk google-android-ndk-installer'
 RUN /bin/bash -c 'apt-get -o=Dpkg::Use-Pty=0 -q -y install wget git pkg-config'
 RUN /bin/bash -c 'git clone https://github.com/Shadowstyler/android-sdk-licenses.git /tmp/android-sdk-licenses && cp -a /tmp/android-sdk-licenses/*-license /usr/lib/android-sdk/licenses && rm -rf /tmp/android-sdk-licenses'
-RUN /bin/bash -c 'apt-get -o=Dpkg::Use-Pty=0 -q -y install automake libtool cmake'
+RUN /bin/bash -c 'apt-get -o=Dpkg::Use-Pty=0 -q -y install automake libtool cmake ccache'