Reduce the path of the build directories used during the tests.
That will remove those CMake warnings:
```
22: CMake Warning in demo/Linear_cell_complex/CMakeLists.txt:
22: The object file directory
22:
22: C:/CGAL/test/CGAL-5.2-Ic-6/cmake/platforms/x64_Cygwin-Windows10_MSVC2017-Release-64bits/test/Installation/build_dir/non_standard_build/demo/Linear_cell_complex/CMakeFiles/Linear_cell_complex_3_demo.dir/
22:
22: has 202 characters. The maximum full path to an object file is 250
22: characters (see CMAKE_OBJECT_PATH_MAX). Object file
22:
22: Linear_cell_complex_3_demo_autogen/mocs_compilation.cpp.obj
22:
22: cannot be safely placed under this directory. The build may not work
22: correctly.
22:
```
https://cgal.geometryfactory.com/CGAL/testsuite/CGAL-5.2-Ic-6/Installation/TestReport_afabri_x64_Cygwin-Windows10_MSVC2017-Release-64bits.gz
https://cgal.geometryfactory.com/CGAL/testsuite/CGAL-5.1-Ic-152/Installation/TestReport_Friedrich_Ubuntu-gcc-7.gz
```
CMake Warning at /home/gimeno/foutoir/cgal_root/CGAL-5.1-Ic-152/cmake/modules/CGAL_enable_end_of_configuration_hook.cmake:99 (message):
=======================================================================
CGAL performance notice:
The variable CMAKE_BUILD_TYPE is set to "". For performance reasons, you
should set CMAKE_BUILD_TYPE to "Release".
Set CGAL_DO_NOT_WARN_ABOUT_CMAKE_BUILD_TYPE to TRUE if you want to disable
this warning.
=======================================================================
Call Stack (most recent call first):
CMakeLists.txt:9223372036854775807 (CGAL_run_at_the_end_of_configuration)
```
right after the merge of 4.14 release branch
+ manual fix on one line in:
* Arrangement_on_surface_2/include/CGAL/IO/Arr_text_formatter.h
* .travis/generate_travis.sh