Fix ctest debian11

This MR makes the test suite pass on Debian 11. A tolerance in flow/tests/adjoint3.py has been slightly increased. Slight modifications in the results seems to be due to another mesh generated by the newer gmsh installed in Debian 11.

I have also added a script to set the environment for building the code with VS2019 on Windows (see scripts/devenv-vs2019.bat)

The full test suite (including Trilinos tests) is OK on Debian 11 (gcc 10.2 - python 3.9).

approved this merge request

merged