fix(native): build Linux binaries against GLIBC 2.28 for RHEL 8 compatibility

[dividedmind]

Build linux-x64 and linux-arm64 inside a custom RHEL 8 UBI container (GCC Toolset 13) so that better_sqlite3.node is compiled against GLIBC 2.28 rather than the host runner's GLIBC 2.39, making the binaries compatible with RHEL 8 / AlmaLinux 8 / Rocky Linux 8.

• ci/Dockerfile.build: new RHEL 8 UBI + GCC 13 builder image, cached in GHCR by Dockerfile SHA via the new sync-builder CI job
• build-native.yml: linux jobs now run inside the builder container; linux-arm64 switches from self-hosted to ubuntu-24.04-arm
• packages/cli/bin/build-native: pass --no-native-build when targeting the current platform (rely on yarn install's compiled addon instead of pkg fetching a pre-built one); derive output name from package.json so the script works for both appmap and scanner
• packages/scanner/bin/build-native: replace duplicate script with a symlink to the cli version

[Copilot]

Pull request overview

This PR updates the native-binary build pipeline so Linux artifacts are produced in a RHEL 8 (GLIBC 2.28) environment, improving compatibility with RHEL/Alma/Rocky 8 while also de-duplicating and generalizing the build-native packaging script across packages.

Changes:

• Add a RHEL 8 UBI + GCC Toolset 13 builder image and a CI job to build/push it to GHCR keyed by the Dockerfile hash.
• Run Linux native builds inside that container (and move linux-arm64 to ubuntu-24.04-arm) to ensure addons are built against GLIBC 2.28.
• Update packages/cli/bin/build-native to derive output name from package.json and skip pkg native-addon rebuilds when targeting the current platform; replace scanner’s duplicate script with a link to the CLI version.

Reviewed changes

Copilot reviewed 2 out of 5 changed files in this pull request and generated 1 comment.

File	Description
ci/Dockerfile.build	Introduces the RHEL 8 builder image (Node 18 + GCC toolset 13) used for Linux native builds.
.github/workflows/build-native.yml	Adds the builder-image sync job and runs Linux builds inside the new container image.
packages/cli/bin/build-native	Generalizes output naming and adds logic to skip pkg native rebuilds for the current platform.
packages/scanner/bin/build-native	De-duplicates by pointing to the CLI build-native script.

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