switch Clang from broken Ubuntu PPA to upstream binary release

This should fix the Travis clang builds

travis-ci/travis-ci#6120

Author: efidler

.travis.yml

@@ -10,16 +10,23 @@ addons:
       - valgrind
 
 env:
-global:
+  global:
     - USE_CCACHE=1
     - CCACHE_SLOPPINESS=pch_defines,time_macros
     - CCACHE_COMPRESS=1
     - CCACHE_MAXSIZE=100M
     - ARCH_FLAGS_x86='-m32'        # #266: don't use SSE on 32-bit
     - ARCH_FLAGS_x86_64='-msse4.2' #       use SSE4.2 on 64-bit
     - GITHUB_REPO='miloyip/rapidjson'
+    - LLVM_VERSION=3.7.1
+    - LLVM_ARCHIVE_PATH=$HOME/clang+llvm.tar.xz
     - secure: "HrsaCb+N66EG1HR+LWH1u51SjaJyRwJEDzqJGYMB7LJ/bfqb9mWKF1fLvZGk46W5t7TVaXRDD5KHFx9DPWvKn4gRUVkwTHEy262ah5ORh8M6n/6VVVajeV/AYt2C0sswdkDBDO4Xq+xy5gdw3G8s1A4Inbm73pUh+6vx+7ltBbk="
 
+before_install:
+    - wget http://llvm.org/releases/${LLVM_VERSION}/clang+llvm-${LLVM_VERSION}-x86_64-linux-gnu-ubuntu-14.04.tar.xz -O ${LLVM_ARCHIVE_PATH}
+    - mkdir ${HOME}/clang-${LLVM_VERSION}
+    - tar xf ${LLVM_ARCHIVE_PATH} -C ${HOME}/clang-${LLVM_VERSION} --strip-components 1
+
 matrix:
   include:
     # gcc
@@ -49,67 +56,55 @@ matrix:
       addons:
         apt:
           sources:
-            - llvm-toolchain-precise-3.7
             - ubuntu-toolchain-r-test
           packages:
             - *default_packages
             - g++-multilib
             - libc6-dbg:i386
-            - clang-3.7
     - env: CONF=debug   ARCH=x86_64 CXX11=ON CCACHE_CPP2=yes
       compiler: clang
       addons:
         apt:
           sources:
-            - llvm-toolchain-precise-3.7
             - ubuntu-toolchain-r-test
           packages:
             - *default_packages
-            - clang-3.7
     - env: CONF=debug   ARCH=x86    CXX11=OFF CCACHE_CPP2=yes
       compiler: clang
       addons:
         apt:
           sources:
-            - llvm-toolchain-precise-3.7
             - ubuntu-toolchain-r-test
           packages:
             - *default_packages
             - g++-multilib
             - libc6-dbg:i386
-            - clang-3.7
     - env: CONF=debug   ARCH=x86_64 CXX11=OFF CCACHE_CPP2=yes
       compiler: clang
       addons:
         apt:
           sources:
-            - llvm-toolchain-precise-3.7
             - ubuntu-toolchain-r-test
           packages:
             - *default_packages
-            - clang-3.7
     - env: CONF=release ARCH=x86    CXX11=ON CCACHE_CPP2=yes
       compiler: clang
       addons:
         apt:
           sources:
-            - llvm-toolchain-precise-3.7
             - ubuntu-toolchain-r-test
           packages:
             - *default_packages
             - g++-multilib
             - libc6-dbg:i386
-            - clang-3.7
     - env: CONF=release ARCH=x86_64 CXX11=ON CCACHE_CPP2=yes
       compiler: clang
       addons:
         apt:
           sources:
-            - llvm-toolchain-precise-3.7
             - ubuntu-toolchain-r-test
           packages:
             - *default_packages
-            - clang-3.7
     # coverage report
     - env: CONF=debug   ARCH=x86    CXX11=ON GCOV_FLAGS='--coverage'
       compiler: gcc
@@ -158,7 +153,7 @@ before_script:
     - mkdir build
 
 script:
-  - if [ "$CXX" = "clang++" ]; then export CXX="clang++-3.7" CC="clang-3.7"; fi
+  - if [ "$CXX" = "clang++" ]; then export CXX="\${HOME}/clang-\${LLVM_VERSION}/bin/clang++" CC="\${HOME}/clang-\${LLVM_VERSION}/bin/clang" CPPFLAGS="-I \${HOME}/clang-\${LLVM_VERSION}/include/c++/v1 \${CPPFLAGS}" CXXFLAGS="-lc++ \${CXXFLAGS}" LD_LIBRARY_PATH="\${HOME}/clang-\${LLVM_VERSION}/lib:\${LD_LIBRARY_PATH}"; fi
   - >
       eval "ARCH_FLAGS=\${ARCH_FLAGS_${ARCH}}" ;
       (cd build && cmake