[SR-1680] More reproducible swift builds


Previous ID	SR-1680
Radar	None
Original Reporter	bnut (JIRA User)
Type	Improvement

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | Project Infrastructure | |Labels | Improvement | |Assignee | None | |Priority | Medium | md5: 8406283366fea63ff5588c73f071ab06

Issue Description:

I'd like a new github repository under `apple/` which is entirely generated by CI, and stores the dependencies that `utils/update-checkout` currently generates. This repository will allow for more reproducible builds.

You can find an example here:
https://github.com/therealbnut/swift-build-requirements

Swift's Incremental Build https://ci.swift.org/job/oss-swift-incremental-RA-osx/ can automatically update the repo for each build configuration that passes:

git-submodules for each swift dependency so you can easily reproduce green CI builds with the exact same dependencies.
structured platform information about which tools were used to build a specific platform.

structured platform information example (incomplete)

osx:
  config: "swift/utils/build-script --preset=buildbot_incremental,tools=RA,stdlib=RA"
  os-version: 10.11.4
  clang: 7.3.0
  ninja: 1.7.1
  ...
ubuntu-14:
  os-version: 14.04
  ...
ubuntu-15:
  os-version: 15.10
  ...

Thanks 🙂

swiftlang / swift

[SR-1680] More reproducible swift builds #44289