Add specific dependencies for Ubuntu 22.04 and provide build example.

• Adds description of required dependencies from a regular desktop install of Ubuntu 22.04 LTS
• Adds suggestion to use mold linker
  • Avoids OOM errors when building OpenVDS with ld
  • Significantly reduces time required to link
• One line fix to code, can be taken out if needed, but removes a dead-store identified with clang-tidy