Dockerfile: update ubuntu 14.04 image with cmake 3.12

.travis.yml

@@ -20,7 +20,7 @@ env:
     # 64-bit UBSan Debug build
     - LINUX_BASE=ubuntu_16.04 C_COMPILER=/usr/bin/clang-3.9 CXX_COMPILER=/usr/bin/clang++-3.9 TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Debug UBSAN_BUILD=1 RUN_UNIT_TESTS=SKIP
     # 64-bit ASan Debug build
-    - LINUX_BASE=ubuntu_16.04 C_COMPILER=/usr/bin/clang-3.9 CXX_COMPILER=/usr/bin/clang++-3.9 TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Debug ASAN_BUILD=1 RUN_UNIT_TESTS=SKIP ASAN_DSO=/usr/lib/clang/3.9/lib/linux/libclang_rt.asan-x86_64.so
+    - LINUX_BASE=ubuntu_16.04 C_COMPILER=/usr/bin/clang-3.9 CXX_COMPILER=/usr/bin/clang++-3.9 TARGET_ARCH=x86_64 Z3_BUILD_TYPE=Debug ASAN_BUILD=1 RUN_UNIT_TESTS=SKIP ASAN_DSO=/usr/lib/clang/3.9/lib/linux/libclang_rt.asan-x86_64.so DOTNET_BINDINGS=0
     # Build for running unit tests under ASan/UBSan
     # FIXME: We should really be doing a debug build but the unit tests run too
     # slowly when we do that.

contrib/ci/Dockerfiles/z3_base_ubuntu_14.04.Dockerfile

@@ -5,7 +5,6 @@ RUN apt-get update && \
         apt-transport-https \
         binutils \
         clang-3.9 \
-        cmake \
         curl \
         doxygen \
         default-jdk \
@@ -31,6 +30,9 @@ RUN curl -SL https://packages.microsoft.com/config/ubuntu/14.04/packages-microso
     apt-get update && \
     apt-get -y --no-install-recommends install dotnet-sdk-2.1
 
+RUN curl -SL https://cmake.org/files/v3.12/cmake-3.12.0-Linux-x86_64.sh --output cmake-3.12.0-Linux-x86_64.sh && \
+    sh cmake-3.12.0-Linux-x86_64.sh --prefix=/usr/local --exclude-subdir
+
 # Create `user` user for container with password `user`.  and give it
 # password-less sudo access
 RUN useradd -m user && \