message: Update clang in RBE dockerfile to the latest release.
diff: @@ -92,6 +92,6 @@ RUN /install/install_pip_packages_by_version.sh "/usr/local/bin/pip3.5"
  RUN /install/install_pip_packages_by_version.sh "/usr/local/bin/pip3.6"
  RUN /install/install_pip_packages_by_version.sh "/usr/local/bin/pip3.7"
  -ENV CLANG_VERSION="r42cab985fd95ba4f3f290e7bb26b93805edb447d"
  +ENV CLANG_VERSION="r7f6f9f4cf966c78a315d15d6e913c43cfa45c47c"
  COPY install/install_latest_clang.sh /install/
  RUN /install/install_latest_clang.sh
  