build: Cache CARGO_HOME again

This was accidentally deleted in 1905a2b5
3 jobs from master in 22 minutes and 52 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Test
passed #52147
flatpak

00:14:47

 
  Deploy
passed #52148
pages

00:08:05

passed pages:deploy

00:00:02