Rollup merge of #87608 - Aaron1011:remove-system-library, r=Mark-Simulacrum
Rollup merge of #87608 - Aaron1011:remove-system-library, r=Mark-Simulacrum

Remove unused field `Session.system_library_path`

aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust