update WRF easyblock to avoid running tests directly in installation directory

[boegel]

(created using eb --new-pr)

[boegel]

Test report by @boegel

Overview of tested easyconfigs (in order)

• FAIL (build issue) WRF-3.9.1.1-intel-2020b-dmpar.eb (partial log available at https://gist.github.com/boegel/ae5f8b5a356e89575c4803293608ddbb)
• FAIL (build issue) WRF-4.2.2-foss-2020b-dmpar.eb (partial log available at https://gist.github.com/boegel/14073c644fa353f65f01b9a605e1cb0b)
• FAIL (build issue) WRF-4.4-foss-2022a-dmpar.eb (partial log available at https://gist.github.com/boegel/367a06ec03a84f07d08615e35b519eb1)
• FAIL (build issue) WRF-4.4.1-foss-2022b-dmpar.eb (partial log available at https://gist.github.com/boegel/a440be41ba3e2dabe9e20f629c7c43e1)

Build succeeded for 0 out of 4 (4 easyconfigs in total)
node3108.skitty.os - Linux RHEL 8.6, x86_64, Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz (skylake_avx512), Python 3.6.8
See https://gist.github.com/boegel/caec900d639619c6083c03a7d4543c9c for a full test report.