Modify rust cache shared-key (#6046)

From reading the action's source code:
1. Job ID is only included if we don't provide da `shared-key`, which I
think we do want to include.
2. OS and architecture always gets added by the actions
3. We should include `RUSTFLAGS` in the cache key, as actions that don't
agree on it will end up re-compiling the world.

---------

Signed-off-by: Adam Gutglick <adam@spiraldb.com>
Co-authored-by: Joe Isaacs <joe.isaacs@live.co.uk>

Author: AdamGS

.github/actions/setup-rust/action.yml

@@ -53,7 +53,9 @@ runs:
       uses: Swatinem/rust-cache@v2
       with:
         save-if: ${{ github.ref_name == 'develop' }}
-        shared-key: "rust-cache-${{ runner.os }}-${{ runner.arch }}-${{ runner.environment }}-${{ steps.rust-toolchain.outputs.cachekey }}-${{ inputs.targets }}${{ inputs.cache-suffix && format('-{0}', inputs.cache-suffix) || '' }}"
+        # os and arch by default
+        shared-key: "rust-cache-${{ github.job }}-${{ runner.environment }}-${{ steps.rust-toolchain.outputs.cachekey }}-${{ inputs.targets }}${{ inputs.cache-suffix && format('-{0}', inputs.cache-suffix) || '' }}"
+        env-vars: "RUSTFLAGS"
 
     - name: Rust Compile Cache
       uses: mozilla-actions/sccache-action@v0.0.9