remove help2man build dependency for flex using system toolchain (because it requires Perl)

[akesandgren]

(created using eb --new-pr)

[akesandgren]

Test report by @akesandgren
SUCCESS
Build succeeded for 2 out of 2 (2 easyconfigs in total)
b-an02.hpc2n.umu.se - Linux Ubuntu 20.04, x86_64, Intel(R) Xeon(R) CPU E5-2690 v4 @ 2.60GHz, Python 3.8.5
See https://gist.github.com/44b678d4fec56c2466601a9050f1a2e4 for a full test report.

[Micket]

Old checksum needs updating to sha256

[akesandgren]

@boegelbot Please test @ generoso

[Micket]

lgtm. In fact, I think we should disable manpages almost everywhere when we can, since we are typically exceeding the max length for MANPATH. I think we should just refer users to the many online documentations for all these softwares instead /rant)

[Micket]

Test report by @Micket
SUCCESS
Build succeeded for 2 out of 2 (2 easyconfigs in total)
alvis-c1 - Linux centos linux 7.9.2009, x86_64, Intel Xeon Processor (Skylake), Python 3.6.8
See https://gist.github.com/b7bdbae1cdbec2c346bf057e342cab38 for a full test report.

[boegelbot]

@akesandgren: Request for testing this PR well received on login1

PR test command 'EB_PR=13922 EB_ARGS= /opt/software/slurm/bin/sbatch --job-name test_PR_13922 --ntasks=4 ~/boegelbot/eb_from_pr_upload_generoso.sh' executed!

• exit code: 0
• output:

Submitted batch job 6772

Test results coming soon (I hope)...

- notification for comment with ID 914290360 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 2 out of 2 (2 easyconfigs in total)
cns2 - Linux rocky linux 8.4, x86_64, Intel(R) Xeon(R) CPU E5-2690 v3 @ 2.60GHz (haswell), Python 3.6.8
See https://gist.github.com/851c7c79c6f67d31751afc07844b355f for a full test report.

[Micket]

Going in, thanks @akesandgren!