A Racket installation includes a "system.rktd" file in the directory reported by (find-lib-dir). When the information in that file does not match the running Racket’s information, then the setup/cross-system module infers that Racket is being run in cross-installation mode.
For example, if an in-place Racket installation for a different platform resides at ‹cross-dir›, then
racket -C -G ‹cross-dir›/etc -X ‹cross-dir›/collects -l- raco pkg
runs raco pkg using the current platform’s racket executable, but using the collections and other configuration information of ‹cross-dir›, as well as modifying the packages of ‹cross-dir›. That can work as long as no platform-specific libraries need to run to perform the requested raco pkg action (e.g., when installing built packages), or as long as the current platform’s installation already includes those libraries.
Added in version 6.3 of package base.
→ (or/c symbol? string? bytes? exact-positive-integer? vector?)
(or/c 'os 'word 'gc 'link 'machine 'so-suffix 'so-mode 'fs-change) = 'os
See also 'cross mode for system-type.
mode : (or/c 'cgc '3m #f) = (system-type 'gc)