fix OpenFOAM 2.3.1-intel-2019b installation on RHEL8

[hajgato]

fixes:

ensight/part/ensightPartIO.C(66): error: identifier "isnan" is undefined
              if (idList[i] >= field.size() || isnan(field[idList[i]]))
                                               ^

ensight/part/ensightPartIO.C(83): error: identifier "isnan" is undefined
              if (isnan(field[i]))
                  ^

and

ensight/part/ensightPart.C(54): error: identifier "isnan" is undefined
              if (id >= field.size() || isnan(field[id]))
                                        ^

[smoors]

@boegelbot please test @ generoso

[boegelbot]

@smoors: Request for testing this PR well received on generoso

PR test command 'EB_PR=11409 EB_ARGS= /apps/slurm/default/bin/sbatch --job-name test_PR_11409 ~/boegelbot/eb_from_pr_upload_generoso.sh' executed!

• exit code: 0
• output:

Submitted batch job 7996

Test results coming soon (I hope)...

- notification for comment with ID 702321587 processed

Message to humans: this is just bookkeeping information for me,
it is of no use to you (unless you think I have a bug, which I don't).

[boegelbot]

Test report by @boegelbot
SUCCESS
Build succeeded for 1 out of 1 (1 easyconfigs in this PR)
generoso-x-5 - Linux centos linux 8.2.2004, x86_64, Intel(R) Xeon(R) CPU E5-2667 v3 @ 3.20GHz (haswell), Python 3.6.8
See https://gist.github.com/55c1cda4eb31ad12864bd42df8617f56 for a full test report.

[smoors]

Test report by @smoors
SUCCESS
Build succeeded for 3 out of 3 (1 easyconfigs in this PR)
node375.hydra.os - Linux centos linux 7.7.1908, x86_64, Intel(R) Xeon(R) Gold 6148 CPU @ 2.40GHz (skylake_avx512), Python 2.7.5
See https://gist.github.com/4c127d7ca6be1a0b29d03969f3b254ef for a full test report.

[smoors]

lgtm

[smoors]

Going in, thanks @hajgato!