turbo

3249e22c - fix: Disable the sccache proxy when remote cache use is off (#13291)

fix: Disable the sccache proxy when remote cache use is off (#13291) ## Why The sccache compile-cache proxy (#13288) gates on an initialized API client, but `should_initialize_http_client()` initializes one whenever credentials merely *look* linked. In CI configurations like this repo's PR jobs — `TURBO_TOKEN=unused`, `TURBO_TEAM=unused`, `TURBO_CACHE=local:rw` — the proxy would start with placeholder credentials, converting every sccache request into a doomed 403 and a visible warning line per compilation unit. ## What One more precondition in `start_sccache_proxy_if_needed`: when remote cache use is disabled for the run (`cache_opts.cache.remote.should_use()` is false), the proxy soft-disables with a debug log, like the other absent-optimization paths. ## How The compile cache *is* the remote cache, so "remote cache off" is a strictly correct reason not to serve it — this also covers `--cache=local:rw` and `TURBO_REMOTE_CACHE_ENABLED=0` generally, not just the placeholder-credentials case. Needed before dogfooding the flag here (the dogfood PR's CI would otherwise spam warnings on every PR run).