fix(ci): Build project using both clang and gcc

.travis.yml

@@ -4,29 +4,26 @@ dist: trusty
 language: cpp
 compiler:
   - clang
-# - gcc
+  - gcc
 cache: ccache
 
 env:
   global:
     - LLVM_VERSION=3.8.0
     - LLVM_ARCHIVE_PATH=$HOME/clang+llvm.tar.xz
-    - CC=$HOME/clang-$LLVM_VERSION/bin/clang
-    - CXX=$HOME/clang-$LLVM_VERSION/bin/clang++
-    - CPPFLAGS="-I $HOME/clang-$LLVM_VERSION/include/c++/v1"
-    - CXXFLAGS="-Qunused-arguments"
 
 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
-  - tar xf $LLVM_ARCHIVE_PATH -C $HOME/clang+llvm --strip-components 1
-  - export PATH=$HOME/clang+llvm/bin:$PATH
+  - mkdir $HOME/clang-$LLVM_VERSION
+  - tar xf $LLVM_ARCHIVE_PATH -C $HOME/clang-$LLVM_VERSION --strip-components 1
+  - export PATH=$HOME/clang-$LLVM_VERSION/bin:$PATH
   - sudo apt-add-repository -y "ppa:george-edison55/george-edison"
   - sudo sed -i "s/trusty/wily/g" /etc/apt/sources.list
   - sudo apt-get -qq update
   - sudo apt-get install -y cmake cmake-data libxrandr-dev libboost-dev libiw-dev libasound2-dev libmpdclient-dev
 
 before_script:
+  - if [ "$CXX" = "clang++" ]; then export CPPFLAGS="-I $HOME/clang-$LLVM_VERSION/include/c++/v1" CXXFLAGS="-Qunused-arguments"; fi
   - cmake --version
   - eval "$CXX --version"
   - eval "$CC --version"