* gnu/packages/patches/racket-gui-tethered-launcher-backport.patch: New
file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/chez-and-racket-bootstrap.scm (racket-vm-for-system): New
procedure.
* gnu/packages/racket.scm (racket-minimal, racket): Update to 8.4.
Rewrite to use 'racket-vm-for-system', label-less inputs, G-expressions,
and Git origins for main-distribution packages.