CI flake: sccache dns lookup failed

[clockwork-labs-bot]

Detected by CI Gremlin after a failed merge-queue run succeeded in a later merge-queue run without a new PR head commit.

Tests:

• Index Scan Bench

Error:
error: process didn't exit successfully: sccache /home/runner/.rustup/toolchains/1.93.0-x86_64-unknown-linux-gnu/bin/rustc -vV (exit status: 2)
--- stderr

Failed job runs:

• https://github.com/clockworklabs/SpacetimeDB/actions/runs/30394268761/job/90398570922 (Index Scan Bench, attempt merge queue run 30394268761 -> merge queue run 30405852929)

Timeout detection:

• none

Context:

• Merge queue PR: Fix TS composite btree range scans #5479
• PR head SHA: 8513489
• Later successful run: https://github.com/clockworklabs/SpacetimeDB/actions/runs/30405852929

[clockwork-labs-bot]

Exact-attempt diagnosis for run 30394268761, job 90398570922, attempt 1:

The Index Scan Bench job checked out the merge-queue ref successfully and reached Run index scan benchmark regression check, but it did not actually get as far as running the benchmark. The first cargo run --release -p spacetimedb-index-scan-gate invocation failed while Cargo was probing the compiler through the sccache wrapper:

error: process didn't exit successfully: `sccache /home/runner/.rustup/toolchains/1.93.0-x86_64-unknown-linux-gnu/bin/rustc -vV` (exit status: 2)
sccache: error: Server startup failed: cache storage failed to read: Unexpected (temporary) at read => send http request
service: ghac
path: .sccache_check
Source: ... client error (Connect): dns error: failed to lookup address information: Try again

Root cause: CI infrastructure/cache connectivity, not an index-scan benchmark regression. The sccache GitHub Actions cache backend could not resolve/connect to the Azure blob cache endpoint during startup, so the compiler wrapper failed before compilation or benchmark execution.

Suggested title: CI infra flake: Index Scan Bench sccache GHAC DNS lookup failed

Duplicate search: I searched the Test Flakes project for exact and broad forms of this mechanism, including sccache rustc -vV exit status 2, sccache rustc, and rustc vV. I did not find another close duplicate in the project. Similar infra/cache flakes may exist, but none from this search were close enough to mark as duplicates.

Top duplicate candidate: none close enough to mark as duplicate.