[build] Export fuchsia_cxx_version variable and .gni file

This provides a way for BUILD.gn files to access the value of the
`experimental_cxx_version` build argument to conditionalize build
logic that needs to match what the C++ source code is doing.  The
new .gni file defines a variable `fuchsia_cxx_version` (not a GN
build argument).  Other BUILD.gn files, especially ones in other
repos, can use this as a quasi-stable part of the internal GN API
that we can leave in place independent of the experimental build
argument.

Bug: 121630
Change-Id: I2c5e01e24ea321284cd96400ff3a97f63756dac1
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/800187
Reviewed-by: Prabhu Karthikeyan Rajasekaran <prabhukr@google.com>
Fuchsia-Auto-Submit: Roland McGrath <mcgrathr@google.com>
Commit-Queue: Auto-Submit <auto-submit@fuchsia-infra.iam.gserviceaccount.com>
2 files changed
tree: 245210afad0c30a1bbc19e87ac87b541c7be6bc5
  1. boards/
  2. build/
  3. bundles/
  4. docs/
  5. examples/
  6. products/
  7. scripts/
  8. sdk/
  9. src/
  10. third_party/
  11. tools/
  12. zircon/
  13. .clang-format
  14. .clang-tidy
  15. .editorconfig
  16. .git-blame-ignore-revs
  17. .gitattributes
  18. .gitignore
  19. .gitmodules
  20. .gn
  21. .style.yapf
  22. analysis_options.yaml
  23. AUTHORS
  24. BUILD.gn
  25. CODE_OF_CONDUCT.md
  26. CONTRIBUTING.md
  27. fuchsia.code-workspace
  28. LICENSE
  29. OWNERS
  30. PATENTS
  31. pyrightconfig.json
  32. README.md
  33. rustfmt.toml
README.md

Fuchsia

What is Fuchsia?

Fuchsia is an open source, general purpose operating system supporting modern 64-bit Intel and ARM processors.

We expect everyone interacting with our project to respect our code of conduct.

Read more about Fuchsia's principles.

How can I build and run Fuchsia?

See Getting Started.

Where can I learn more about Fuchsia?

See fuchsia.dev.