using shell as entrypoint

Dockerfile

 FROM openjdk:8
 WORKDIR /ragdoc-builder
+COPY .gradle /ragdoc-builder/.gradle
+COPY gradle /ragdoc-builder/gradle
+COPY gradlew /ragdoc-builder/
+RUN ls -lha
+RUN chmod +x ./gradlew && ./gradlew --no-daemon --version
 ADD . /ragdoc-builder/
-RUN chmod +x ./gradlew start-builder.sh && ./gradlew --no-daemon --version
-RUN ./gradlew fatJar && rm -r gradle/ extendj/ src/ build/ gradlew build.gradle settings.gradle
+RUN chmod +x start-builder.sh
+RUN ./gradlew --no-daemon fatJar && rm -r gradle/ extendj/ src/ build/ gradlew build.gradle settings.gradle
 ENV BOOT_CLASSPATH="/usr/local/openjdk-8/jre/lib/rt.jar"
 VOLUME ["/src"]
 VOLUME ["/data"]
 # ENTRYPOINT ["java", "-jar", "rd-builder.jar", "-d", "/data", "-bootclasspath", "$BOOT_CLASSPATH", "/src/*"]
-ENTRYPOINT ["./start-builder.sh"]
+# ENTRYPOINT ["./start-builder.sh"]
+ENTRYPOINT ["/bin/sh"]

start-builder.sh

 #!/bin/sh
-TARGET=${1:-/data}
-SOURCE=${2:-/src/}
-JAVA_FILES=$(find $SOURCE -name '*.java')
-java -jar rd-builder.jar -d $TARGET -bootclasspath $BOOT_CLASSPATH $JAVA_FILES
+java -jar rd-builder.jar -bootclasspath $BOOT_CLASSPATH $@