How to Change the SHELL on Building the DOCKER Image

RUN echo I am using the default (/bin/sh)
RUN ["/bin/bash", "-c", "echo I am using bash"]
SHELL ["/bin/bash", "-c"]
RUN echo I am using bash, which is now the default
RUN ["/bin/sh", "-c", "echo I am using /bin/sh"]
RUN ["echo", "I don't use a shell at all"]