How to install clang with C++17 on Travis CI?

I'm trying to setup Trevis CI with clang 4.0. I need C++17 support. I use following script:

language: cpp
sudo: required

os:
    - linux

compiler:
    - clang

env:
    - TARGET_CPU=x86 BUILD_CONFIGURATION=Debug
    - TARGET_CPU=x86 BUILD_CONFIGURATION=Release
    - TARGET_CPU=x64 BUILD_CONFIGURATION=Debug
    - TARGET_CPU=x64 BUILD_CONFIGURATION=Release
    - TARGET_CPU=amd64 BUILD_CONFIGURATION=Debug
    - TARGET_CPU=amd64 BUILD_CONFIGURATION=Release

before_install:  
  - sudo apt-add-repository "deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-4.0 main"
  - sudo apt-get update -qq

install: 
  - sudo apt-get install libboost-all-dev
  - sudo apt-get install --allow-unauthenticated -qq clang++-4.0
  - export CXX="clang++-4.0"

script:
    - mkdir build
    - cd build
    - cmake .. -DTARGET_CPU=$TARGET_CPU -DCMAKE_BUILD_TYPE=$BUILD_CONFIGURATION
    - make

Despite of clang 4.0 was successfully installed build fails with message: error: no member named 'make_unique' in namespace 'std'. It means I have even no C++11 support. How I can fix it? Did I miss something in travis.yml?