run combined build only

There is no need for separate 'googlemock' and 'googletest' builds,
as the 'googlemock' build includes 'googletest' and it's unit tests.

travis.sh

@@ -3,13 +3,12 @@ set -evx
 env | sort
 
 mkdir build || true
-mkdir build/$GTEST_TARGET || true
-cd build/$GTEST_TARGET
+cd build
 cmake -Dgtest_build_samples=ON \
       -Dgmock_build_samples=ON \
       -Dgtest_build_tests=ON \
       -Dgmock_build_tests=ON \
       -DCMAKE_CXX_FLAGS=$CXX_FLAGS \
-      ../../$GTEST_TARGET
+      ..
 make
 CTEST_OUTPUT_ON_FAILURE=1 make test