[travis] Make cmake verbose

.travis/build

@@ -20,6 +20,10 @@ export LD_LIBRARY_PATH="$install_dir/lib/`dpkg-architecture -qDEB_BUILD_MULTIARC
 export PKG_CONFIG_PATH="$install_dir/lib/pkgconfig:$PKG_CONFIG_PATH"
 export PKG_CONFIG_PATH="$install_dir/lib/`dpkg-architecture -qDEB_BUILD_MULTIARCH`/pkgconfig:$PKG_CONFIG_PATH"
 
+# Make cmake verbose.
+export CMAKE_VERBOSE_MAKEFILE=1
+export CTEST_OUTPUT_ON_FAILURE=1
+
 install_dependency()
 {
     echo "--> Compiling $1"