fix: add linux-x64-baseline target mapping to build script

[err0x420]

Re-opening PR #814 following the repository history rewrite, as requested by maintainers.

Summary

The 'linux-x64-baseline' target mapping was missing from cli/scripts/build-binary.ts, preventing the build pipeline from mapping and producing the baseline binary artifact.

Details

• Adds 'linux-x64-baseline' (mapped to 'bun-linux-x64-baseline') to getTargetInfo().
• The CLI client runtime (index.js) already contains the fallback logic and looks for freebuff-linux-x64-baseline.tar.gz.
• Adding this mapping allows the build script to properly resolve bun-linux-x64-baseline.

Fixes #797
Ref #814

[codebuff-team]

This is a small, targeted change that adds linux-x64-baseline and win32-x64-baseline entries to getTargetInfo() in cli/scripts/build-binary.ts, matching the pattern of existing entries (linux-x64, win32-x64, etc.). The rationale is credible: the runtime fallback logic in index.js already expects a freebuff-linux-x64-baseline.tar.gz artifact, so without this mapping the build script can't produce it, referencing issue #797.

A few things worth checking before porting:

• The PR title/summary only mention linux-x64-baseline, but the diff also adds win32-x64-baseline. Please update the description to cover both, since a reviewer skimming the summary would miss half the change.
• No test or build verification is shown - it'd help to confirm these bun targets (bun-linux-x64-baseline, bun-windows-x64-baseline) are valid Bun compile targets and that CI can actually produce these artifacts, since a typo here would fail silently until someone tries to build for baseline CPUs.
• Given this references two prior PRs (fix: add linux-x64-baseline target to build script #814, linux-x64-baseline target still contains AVX instructions, causing SIGILL on older CPUs (SSE4.1 only) #797), it'd be useful to link what discussion happened there so the maintainer porting this doesn't have to reconstruct context from scratch.

Overall the change itself is small, in-scope, and plausible - worth a maintainer's time to verify against the actual Bun target list and port.