[FIX] Dockerfile: add env var to avoid numpy weird errors

Description of the issue/feature this PR addresses:

Currently, if numpy is available in the modules even if you are not using it Odoo try to compile and the system is down only for a type of processor

Currently we know 2 server reproducing the error:

• B&F-production
• Runbot

More info about:

https://github.com/numpy/numpy/issues/17674 https://github.com/numpy/numpy/pull/17759

It is reproducing in the following MR:

https://git.vauxoo.com/vauxoo/lasec/-/merge_requests/197

Check the following discussion https://odoo-community.org/groups/contributors-15/contributors-186006?mode=thread&date_begin=&date_end=

OpenBLAS creates a number of threads equal to the number of core threads available: 56 in my case (production server), so it quickly reached limit_memory_hard and the process was killed (SIGSEGV) Forcing OPENBLAS_NUM_THREADS=1 fixed the issue.

Current behavior before PR: Weird errors related to numpy.

Desired behavior after PR is merged: No errors related to numpy.

Close #85

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