message: [ci] Add rust-toolchain to cache key
  This will prevent caching artifacts across Rust compiler versions
  Closes:
  Approved by: rexhoffman
diff: @@ -122,10 +122,12 @@ commands:
  - run:
  name: Generate date code for cache key
  # NOTE circle's built-in key does not support date
  - command: date +%Y%m%d > /tmp/date
  + command: |
  + cat rust-toolchain > /tmp/cache-key
  + date +%Y%m%d >> /tmp/cache-key
  - save_cache:
  name: Save sccache
  - key: sccache-{{ .Environment.CIRCLE_JOB }}-{{ checksum "/tmp/date" }}
  + key: sccache-{{ .Environment.CIRCLE_JOB }}-{{ checksum "/tmp/cache-key" }}
  paths:
  - "/home/circleci/.cache/sccache"
  restore_sccache:
  @@ -133,10 +135,12 @@ commands:
  steps:
  - run:
  name: Generate date code for cache key
  - command: date +%Y%m%d > /tmp/date
  + command: |
  + cat rust-toolchain > /tmp/cache-key
  + date +%Y%m%d >> /tmp/cache-key
  - restore_cache:
  name: Restore sccache
  - key: sccache-{{ .Environment.CIRCLE_JOB }}-{{ checksum "/tmp/date" }}
  + key: sccache-{{ .Environment.CIRCLE_JOB }}-{{ checksum "/tmp/cache-key" }}
  - run:
  name: Show sccache
  command: sccache -s
  