Lmod: Create Custom SitePackage.lua in RC Path to Override RPM Installed File

In #526 (closed), the Bright Lmod RPM package caught us off guard by overwriting our customized /usr/share/lmod/7.8.11/libexec/SitePackage.lua file with its default one.

To avoid it, we should consider building our own Lmod package to include customized settings like the SitePackage.lua file and spider cache settings or investigate if it's possible to override the default location of this file.