ReserveCacheError: Unable to reserve cache with key <cache-key>

When using a reusable build inside a matrix workflow, only one of the jobs is able to write its cache.

example:

```yaml
# .github/workflows/main.yaml

on:
push: [main]

jobs:
build-android:
strategy:
matrix:
app-name:
- app1
- app2
uses: ./.github/workflows/reusable-build.yaml
with:
app-name: ${{ matrix.app-name }}
```

```yaml
# .github/workflows/reusable-build.yaml

on:
workflow_call:
inputs:
app-name:
required: true
type: string
jobs:
build:
steps:

# ...

- uses: gradle/actions/setup-gradle@v4

# ... build
```

In the example above, one of the gradle steps will successfully write its cache, but the other fails with error

```
Failed to save cache entry with path '' and key: : ReserveCacheError: Unable to reserve cache with key , another job may be creating this cache.
```

Both jobs have the same key. Edit: the cache key doesn't include anything for the matrix context (eg `gradle-home-v1|Linux-X64|build[ef6094c74d56794d327380021ca7a151]-2baefdce1c4b89355ff1a945a35e960b6289568f`)

Reproduce the matrix workflow from .github/workflows/main.yaml and .github/workflows/reusable-build.yaml, focusing on the gradle/actions/setup-gradle@v4 step. Compare the cache keys and reservation behavior across the matrix jobs. Done means the cause of the conflicting cache writes is confirmed and covered by an agreed fix, regression test, or documented limitation.

Written by the indexing model from the issue text.