failing installation of Net::SSLeay extension in Perl/5.34.1/GCCcore-11.3.0 in EESSI 2023.04 (related to OpenSSL)

[boegel]

== 2023-06-07 06:55:57,644 run.py:217 DEBUG run_cmd: running cmd export OPENSSL_PREFIX=$EBROOTOPENSSL &&  perl Makefile.PL PREFIX=/cvmfs/pilot.eessi-hpc.org/versions/2023.04/software/linux/x86_64/amd/zen3/software/Perl/5.34.1-GCCcore-11.3.0  (in /tmp/easybuild/build/Perl/5.34.1/GCCcore-11.3.0/NetSSLeay/Net-SSLeay-1.92)
...
== 2023-06-07 06:55:57,769 build_log.py:171 ERROR EasyBuild crashed with an error (at easybuild/tools/build_log.py:111 in caller_info): cmd "export OPENSSL_PREFIX=$EBROOTOPENSSL &&  perl Makefile.PL PREFIX=/cvmfs/pilot.eessi-hpc.org/versions/2023.04/software/linux/x86_64/amd/zen3/software/Perl/5.34.1-GCCcore-11.3.0 " exited with exit code 1 and output:
...
* COULD NOT FIND LIBSSL HEADERS                                              *
*                                                                            *
* The libssl header files are required to build Net-SSLeay, but they are     *
* missing from . They would typically reside in /include/openssl.            *

May be due to OpenSSL 3.0.x in 2023.04 compat layer, or could be self-inflicted because we're filtering the OpenSSL/1.1 dependency (cfr. #256), which leads to $EBROOTOPENSSL not being defined.

[boegel]

Problem fixed in new EESSI pilot version 2023.06 by sticking to OpenSSL 1.1.1 for now in compat layer, cfr. EESSI/compatibility-layer#188