Enable PGO for Linux x86-64 uv releases (#21001)
## Summary
This PR enables PGO for uv releases, starting with Linux x86-64.
### Design
The release pipeline is modified as follows:
- We build instrumented `uv` and `uvx` release binaries inside the
existing manylinux container.
- We train directly on eleven shared `test/ecosystem` fixtures:
cibuildwheel, Cookiecutter, Flask, HTTPX, LLM, the OpenAI Python SDK,
Poetry, pytest-cov, Sentry, Zulip, and the 38-project pyx workspace.
- Every project exercises cold and warm `uv pip compile` resolution,
cold and warm `uv lock` resolution, `uv export`, `uv pip` installation,
and `uv sync` installation on every release platform.
- Per-project `exclude-dependencies` settings omit packages without
compatible release-platform wheels while preserving the rest of each
real dependency graph.
- Raw profiles are merged online by workload family, then merged with
`llvm-profdata` and fed back into the existing `maturin` build.
- JupyterLab, Saleor, Semantic Kernel, Transformers, and Warehouse
remain separate, held-out evaluation projects.
### Results
We benchmarked the builds on Linux x86-64 using the expanded corpus for
training and five separate held-out ecosystem projects for evaluation.
| Held-out project | Dependency resolution | Wheel installation |
Project locking | Lockfile export |
| ---------------- | --------------------: | -----------------: |
---------------: | --------------: |
| JupyterLab | 11.2% faster | 0.0% | 10.1% faster | 10.6% faster |
| Semantic Kernel | 9.3% faster | 7.1% faster | 12.5% faster | 8.7%
faster |
| Transformers | 11.7% faster | 4.1% faster | 9.5% faster | 11.0% faster
|
| Saleor | — | — | 9.7% faster | 10.0% faster |
| Warehouse | — | — | 9.7% faster | 7.6% faster |
| Geometric mean | **10.7% faster** | **3.7% faster** | **10.3% faster**
| **9.6% faster** |
Across all sixteen held-out workloads, wall time decreased by **8.9%**
(95% CI: 8.4–9.8%) and CPU time decreased by **8.4%** (95% CI:
7.9–9.0%). The matched Linux executable was **13.3% smaller** (58.91 MB
to 51.05 MB), or **12.3% smaller** after gzip compression (22.68 MB to
19.90 MB).
(Saleor and Warehouse include source-only dependencies, so they are
benchmarked on locking and export rather than wheel-only installation.)
### Stack
Additional platforms are covered in subsequent PRs in the stack: macOS
ARM64, Windows x86-64, and Linux ARM64.
Ruff and ty follow the same approach; see the stacks here:
- https://github.com/astral-sh/ruff/pull/27570
- https://github.com/astral-sh/ty/pull/4213
