Fix a bug where the GUI could not be closed

IN16B QENS improvements

Recognise new SYSTEST_NPROCS variable in systemtest scripts

Add script repository in workbench

We have been using DragNDrop packages on macOS for some time
and this just requires `cp` and not the use of `installer`.

Use CMake generated export headers in additional libraries

Adding ALF view

Update CG2 (GPSANS) instrument definition file

Signed-off-by: Jose Borreguero <borreguero@gmail.com>

Fix z-offsets check and monitor saving

Instead of sharing the BUILD_THREADS allow a second variable
to define how many processes are used to run the system tests.
Some systems can get overloaded if too many system tests are
run in parallel but we don't want to reduce the concurrency
for the build process

Apply placzek correction to polaris workflow

Co-Authored-By: Harrietbrown <49688535+Harrietbrown@users.noreply.github.com>