Try to set libc++ in cmake

.travis.yml

@@ -155,7 +155,7 @@ before_script:
     - mkdir build
 
 script:
-  - if [ "$CXX" = "clang++" ]; then export CXX="clang++-3.7" CXXFLAGS="-stdlib=libc++" CC="clang-3.7"; fi
+  - if [ "$CXX" = "clang++" ]; then export CXX="clang++-3.7" CC="clang-3.7"; fi
   - >
       eval "ARCH_FLAGS=\${ARCH_FLAGS_${ARCH}}" ;
       (cd build && cmake

example/CMakeLists.txt

@@ -25,7 +25,7 @@ add_definitions(-D__STDC_FORMAT_MACROS)
 if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror -Wall -Wextra -Weffc++ -Wswitch-default")
 elseif (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror -Wall -Wextra -Weffc++ -Wswitch-default -Wfloat-equal -Wimplicit-fallthrough -Weverything")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++ -Werror -Wall -Wextra -Weffc++ -Wswitch-default -Wfloat-equal -Wimplicit-fallthrough -Weverything")
 elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
     add_definitions(-D_CRT_SECURE_NO_WARNINGS=1)
 endif()