build: use OpenJDK 8 instead of Oracle's version

Fixes #57

Dockerfile

@@ -15,8 +15,7 @@ ENV	ANDROID_APIS="android-26" \
   ANDROID_SDK_TOOLS_DOWNLOAD_URL="https://dl.google.com/android/repository/sdk-tools-linux-3859397.zip" \
   GOOGLE_SIGNING_KEY_URL="https://dl-ssl.google.com/linux/linux_signing_key.pub" \
   GOOGLE_CHROME_REPOSITORY_URL="http://dl.google.com/linux/chrome/deb/" \
-  ### Java and android SDK paths
-  JAVA_HOME="/usr/lib/jvm/java-8-oracle" \
+  ### Android SDK path
   ANDROID_HOME="/opt/android-sdk" \
   ### Installation files
   SCRIPTS_DIRECTORY="scripts" \
@@ -36,6 +35,10 @@ RUN	rm /bin/sh && ln -s /bin/bash /bin/sh && \
   ### Set debconf to run non-interactively
   echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections
 
+### Install JAVA 8
+RUN apt-get update && \
+  apt-get install --no-install-recommends -y openjdk-8-jdk
+
 ### Install locales and base dependencies
 RUN	apt-get update && \
   apt-get install -y --no-install-recommends \
@@ -47,6 +50,7 @@ RUN	apt-get update && \
   libssl-dev \
   git \
   gradle \
+  ca-certificates-java \
   python \
   software-properties-common \
   ssh \
@@ -66,17 +70,9 @@ RUN dpkg-reconfigure --frontend noninteractive locales
 RUN wget -q -O - $GOOGLE_SIGNING_KEY_URL | apt-key add -
 RUN echo "deb $GOOGLE_CHROME_REPOSITORY_URL stable main" >> /etc/apt/sources.list.d/google.list
 
-### Install JAVA
-RUN add-apt-repository ppa:webupd8team/java -y && \
-  apt-get update -y && \
-  echo debconf shared/accepted-oracle-license-v1-1 select true | \
-  debconf-set-selections && \
-  echo debconf shared/accepted-oracle-license-v1-1 seen true | \
-  debconf-set-selections && \
+### Install Chrome
+RUN apt-get update -y && \
   apt-get install -y --no-install-recommends \
-  oracle-java8-installer \
-  oracle-java8-set-default \
-  ca-certificates-java \
   ### Install chrome and virtual frame buffer
   google-chrome-stable xvfb && \
   ### Clear apt cache