fix permission issues when copying xvfb-run script in Xvfb easyconfigs

[boegel]

(created using eb --new-pr)

This fixes problems with the cp -a command in certain setups, in particular in the EESSI build environment (see also EESSI/software-layer#299):

cp: preserving permissions for '/cvmfs/pilot.eessi-hpc.org/versions/2023.06/software/linux/aarch64/neoverse_n1/software/Xvfb/1.20.11-GCCcore-10.3.0/bin/xvfb-run': Permission denied

[boegel]

@boegelbot please test @ generoso

[boegelbot]

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

PR test command 'EB_PR=18834 EB_ARGS= EB_CONTAINER= EB_REPO=easybuild-easyconfigs /opt/software/slurm/bin/sbatch --job-name test_PR_18834 --ntasks=4 ~/boegelbot/eb_from_pr_upload_generoso.sh' executed!

• exit code: 0
• output:

Submitted batch job 11743

Test results coming soon (I hope)...

- notification for comment with ID 1725549256 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 9 out of 9 (9 easyconfigs in total)
cns1 - Linux Rocky Linux 8.5, x86_64, Intel(R) Xeon(R) CPU E5-2667 v3 @ 3.20GHz (haswell), Python 3.6.8
See https://gist.github.com/boegelbot/a7d02f1ae6a5bcda96af9d1fc9c49187 for a full test report.

[ocaisa]

@boegelbot please test @ jsc-zen2

[boegelbot]

@ocaisa: Request for testing this PR well received on jsczen2l1.int.jsc-zen2.easybuild-test.cluster

PR test command 'EB_PR=18834 EB_ARGS= EB_REPO=easybuild-easyconfigs /opt/software/slurm/bin/sbatch --mem-per-cpu=4000M --job-name test_PR_18834 --ntasks=8 ~/boegelbot/eb_from_pr_upload_jsc-zen2.sh' executed!

• exit code: 0
• output:

Submitted batch job 3391

Test results coming soon (I hope)...

- notification for comment with ID 1725712073 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
FAILED
Build succeeded for 9 out of 11 (9 easyconfigs in total)
jsczen2g1.int.jsc-zen2.easybuild-test.cluster - Linux Rocky Linux 8.5, x86_64, AMD EPYC 7742 64-Core Processor (zen2), Python 3.6.8
See https://gist.github.com/boegelbot/abde9fc517698175a4d3d1f566fb1310 for a full test report.

[ocaisa]

The failing build on jsczen2 was for python and not related to this PR, merging