Use custom runner for building CLI (#3716)

# Description of Changes

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here. -->

- This has 2 benefits:
1. `ubuntu-latest` recently changed to 24.04 instead of 22.04 so that
broke the last CLI on some systems. This will fix that issue.
2. Performance - this should build much much faster.

# API and ABI breaking changes

None

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corresponding GitHub label. -->

# Expected complexity level and risk

2 - if the CLI fails to build this might be why.

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# Testing

- [x] Tested via today's release:
https://github.com/clockworklabs/SpacetimeDB/actions/runs/19550648024/job/55980960439

Author: jdetter

.github/workflows/package.yml

@@ -14,7 +14,13 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - { name: x86_64 Linux, target: x86_64-unknown-linux-gnu, runner: ubuntu-latest }
+          - name: x86_64 Linux
+            target: x86_64-unknown-linux-gnu
+            runner: spacetimedb-new-runner
+            container:
+              image: localhost:5000/spacetimedb-ci:latest
+              options: >-
+                --privileged
           - { name: aarch64 Linux, target: aarch64-unknown-linux-gnu, runner: arm-runner }
           # Disabled because musl builds weren't working and we didn't want to investigate. See https://github.com/clockworklabs/SpacetimeDB/pull/2964.
           # - { name: x86_64 Linux musl, target: x86_64-unknown-linux-musl, runner: bare-metal, container: alpine }