gpu_cache: Clarify rebuild docs

10 jobs for master in 17 minutes and 2 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #18459
build:nightly

00:01:24

passed #18460
build:nightly:gpu_cache

00:01:29

passed #18461
build:redox

00:01:26

passed #18457
build:stable

00:01:27

passed #18458
build:stable:gpu_cache

00:01:31

 
  Test
passed #18465
test:benches

00:05:44

passed #18464
test:nightly

00:05:32

passed #18466
test:nightly:gpu_cache

00:03:39

passed #18462
test:stable

00:05:49

passed #18463
test:stable:gpu_cache

00:06:23