[Travis] Disable clang for the moment.

On making tests fails with:

../bin/testrunner: error while loading shared libraries: libomp.so:
    cannot open shared object file: No such file or directory

.travis.yml

@@ -31,12 +31,12 @@ matrix:
   include:
     - compiler: gcc
       env: CASE=CLI CMAKE_ARGS="-DOGS_BUILD_GUI=OFF -DOGS_BUILD_UTILS=ON"
-    - compiler: clang
-      env: CASE=CLI CMAKE_ARGS="-DOGS_BUILD_GUI=OFF -DOGS_BUILD_UTILS=ON"
+    # - compiler: clang
+    #   env: CASE=CLI CMAKE_ARGS="-DOGS_BUILD_GUI=OFF -DOGS_BUILD_UTILS=ON"
     - compiler: gcc
       env: CASE=GUI CMAKE_ARGS="-DOGS_BUILD_GUI=ON -DOGS_BUILD_CLI=OFF -DOGS_BUILD_TESTS=ON -DCMAKE_POSITION_INDEPENDENT_CODE=ON"
-    - compiler: clang
-      env: CASE=GUI CMAKE_ARGS="-DOGS_BUILD_GUI=ON -DOGS_BUILD_CLI=OFF -DOGS_BUILD_TESTS=ON -DCMAKE_POSITION_INDEPENDENT_CODE=ON"
+    # - compiler: clang
+    #   env: CASE=GUI CMAKE_ARGS="-DOGS_BUILD_GUI=ON -DOGS_BUILD_CLI=OFF -DOGS_BUILD_TESTS=ON -DCMAKE_POSITION_INDEPENDENT_CODE=ON"
     # - compiler: gcc
     #   env: CASE=CONAN CMAKE_ARGS="-DOGS_BUILD_GUI=ON -DOGS_BUILD_UTILS=ON"
     - compiler: gcc