regenerate dockerfiles

tools/dockerfile/test/cxx_jessie_x64/Dockerfile

@@ -73,9 +73,14 @@ RUN pip install futures==2.2.0 enum34==1.0.4 protobuf==3.5.2.post1 six==1.10.0 t
 RUN apt-get update && apt-get -y install libgflags-dev libgtest-dev libc++-dev clang && apt-get clean
 
 #=================
-# Update clang to a version with improved tsan and fuzzing capabilities
+# 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
 
-RUN apt-get update && apt-get -y install python 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 ..

tools/dockerfile/test/fuzzer/Dockerfile

@@ -73,9 +73,14 @@ RUN pip install futures==2.2.0 enum34==1.0.4 protobuf==3.5.2.post1 six==1.10.0 t
 RUN apt-get update && apt-get -y install libgflags-dev libgtest-dev libc++-dev clang && apt-get clean
 
 #=================
-# Update clang to a version with improved tsan and fuzzing capabilities
+# 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
 
-RUN apt-get update && apt-get -y install python 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 ..