force libdir to be part of our execution environment

[evgeni]

When the kafo is executed on a system that itself is a client to a Puppet
server, plugins that got synced (using pluginsync) from said server into
/opt/puppetlabs/puppet/cache/lib/ are picked up instead of the ones in
the configured modules dir under certain circumstances.

For example, puppetlabs-postgresql changed the postgresql_conf provider
from "parsed" to "ruby" in 10.0. If the parsed provider is present in
/opt/puppetlabs/puppet/cache/lib/ it gets used, instead of the new ruby
one, but the calling code (being from puppetlabs-postgresql 10+) doesn't
expect that and fails to properly (yet silently!) configure PostgreSQL.

[evgeni]

For those who want to reproduce this at home, but do not want to hook up to an external Puppet server:

1. poison the cache:

# mkdir -p /opt/puppetlabs/puppet/cache/lib/puppet/provider/postgresql_conf/
# curl -o /opt/puppetlabs/puppet/cache/lib/puppet/provider/postgresql_conf/parsed.rb https://raw.githubusercontent.com/puppetlabs/puppetlabs-postgresql/refs/tags/v9.2.0/lib/puppet/provider/postgresql_conf/parsed.rb

2. set max_connections to something silly (like "5") in /var/lib/pgsql/data/postgresql.conf
3. run the installer
4. verify that the value is unchanged

# grep max_con /var/lib/pgsql/data/postgresql.conf 
max_connections = 5

and the "parsed" provider was used

# grep "Prefetching parsed" /var/log/foreman-installer/*.log 
2025-06-03 11:44:02 [DEBUG ] [configure] Prefetching parsed resources for postgresql_conf

5. apply patch
6. run the installer again
7. verify the value is changed

# grep max_con /var/lib/pgsql/data/postgresql.conf 
max_connections = 500

the "parsed" provider was not used

# grep "Prefetching parsed" /var/log/foreman-installer/*.log 
<empty>

the output of the new, ruby, provider is visible

# grep "parse_config Active Settings" /var/log/foreman-installer/*.log
2025-06-03 11:46:42 [DEBUG ] [configure] DEBUG: parse_config Active Settings found in PostgreSQL config file: …