Remove installed from source Clang in standard Jessie Dockerfile

templates/tools/dockerfile/test/cxx_jessie_x64/Dockerfile.template

@@ -20,8 +20,6 @@
   <%include file="../../gcp_api_libraries.include"/>
   <%include file="../../python_deps.include"/>
   <%include file="../../cxx_deps.include"/>
-  <%include file="../../cmake_jessie_backports.include"/>
-  <%include file="../../clang_update.include"/>
   <%include file="../../run_tests_addons.include"/>
   <%include file="../../libuv_install.include"/>
 

tools/dockerfile/test/cxx_jessie_x64/Dockerfile

@@ -72,44 +72,6 @@ RUN pip install futures==2.2.0 enum34==1.0.4 protobuf==3.5.2.post1 six==1.10.0 t
 # C++ dependencies
 RUN apt-get update && apt-get -y install libgflags-dev libgtest-dev libc++-dev clang && apt-get clean
 
-#=================
-# Use cmake 3.6 from jessie-backports
-# should only be used for images based on debian jessie.
-
-RUN echo "deb http://ftp.debian.org/debian jessie-backports main" | tee /etc/apt/sources.list.d/jessie-backports.list
-RUN apt-get update && apt-get install -t jessie-backports -y cmake && apt-get clean
-
-#=================
-# Update clang to a version with improved tsan and fuzzing capabilities
-
-RUN git clone -n -b release_38 http://llvm.org/git/llvm.git && \
-  cd llvm && git checkout ad57503 && cd ..
-RUN git clone -n -b release_38 http://llvm.org/git/clang.git && \
-  cd clang && git checkout ad2c56e && cd ..
-RUN git clone -n -b release_38 http://llvm.org/git/compiler-rt.git && \
-  cd compiler-rt && git checkout 3176922 && cd ..
-RUN git clone -n -b release_38 \
-  http://llvm.org/git/clang-tools-extra.git && cd clang-tools-extra && \
-  git checkout c288525 && cd ..
-RUN git clone -n -b release_38 http://llvm.org/git/libcxx.git && \
-  cd libcxx && git checkout fda3549  && cd ..
-RUN git clone -n -b release_38 http://llvm.org/git/libcxxabi.git && \
-  cd libcxxabi && git checkout 8d4e51d && cd ..
-
-RUN mv clang llvm/tools
-RUN mv compiler-rt llvm/projects
-RUN mv clang-tools-extra llvm/tools/clang/tools
-RUN mv libcxx llvm/projects
-RUN mv libcxxabi llvm/projects
-
-RUN mkdir llvm-build
-RUN cd llvm-build && cmake \
-  -DCMAKE_BUILD_TYPE:STRING=Release \
-  -DCMAKE_INSTALL_PREFIX:STRING=/usr \
-  -DLLVM_TARGETS_TO_BUILD:STRING=X86 \
-  ../llvm
-RUN make -C llvm-build -j 12 && make -C llvm-build install && rm -rf llvm-build
-
 
 RUN mkdir /var/local/jenkins