Fix cache_dir path for ccache config (#8370)

Previously we are missing `ccache --set-config=cache_dir="$ccache_dir"`
and the build was using the default cache_dir.
This PR fixed that and the cache are hit in reruns.

```
📊 ccache statistics (post-build):
Cacheable calls:    1198 / 1198 (100.0%)
  Hits:             1195 / 1198 (99.75%)
    Direct:         1193 / 1195 (99.83%)
    Preprocessed:      2 / 1195 ( 0.17%)
  Misses:              3 / 1198 ( 0.25%)
Local storage:
  Cache size (GiB):  0.6 /  5.0 (11.11%)
  Hits:             1195 / 1198 (99.75%)
  Misses:              3 / 1198 ( 0.25%)
```

0 files changed, 0 insertions, 0 deletions