Use clang-3.5 since the Travis version has a conflict with gcc (check this issue https://bugs.debian.org/cgi-bin/bugreport.cgi?msg=11;bug=744872)

Kirill V. Lyadvinsky · Kirill V. Lyadvinsky · commit 89aa87bd245a · 2016-11-09T12:05:22.000+03:00
diff --git a/.gitignore b/.gitignore
@@ -30,8 +30,7 @@
 
 # CMake-generated files:
 CMakeFiles/
-CTestTestFile.cmake
-cmake_install.cmake
+*.cmake
 pkg-config/jsoncpp.pc
 jsoncpp_lib_static.dir/
 
@@ -45,6 +44,7 @@ jsoncpp_lib_static.dir/
 /src/lib_json/Makefile
 /src/test_lib_json/Makefile
 /src/test_lib_json/jsoncpp_test
+*.a
 
 # eclipse project files
 .project
diff --git a/.travis.yml b/.travis.yml
@@ -9,8 +9,8 @@
 install:
 # /usr/bin/gcc is 4.6 always, but gcc-X.Y is available.
 - if [ "$CXX" = "g++" ]; then export CXX="g++-4.9" CC="gcc-4.9"; fi
-# /usr/bin/clang is our version already, and clang-X.Y does not exist.
-#- if [ "$CXX" = "clang++" ]; then export CXX="clang++-3.7" CC="clang-3.7"; fi
+# /usr/bin/clang has a conflict with gcc, so use clang-X.Y.
+- if [ "$CXX" = "clang++" ]; then export CXX="clang++-3.5" CC="clang-3.5"; fi
 - echo ${PATH}
 - ls /usr/local
 - ls /usr/local/bin
@@ -22,10 +22,11 @@ addons:
   apt:
     sources:
     - ubuntu-toolchain-r-test
+    - llvm-toolchain-precise-3.5
     packages:
     - gcc-4.9
     - g++-4.9
-    - clang
+    - clang-3.5
     - valgrind
 os:
   - linux
