Make LTO an option in gen.py

Previously, LTO was enabled unconditionally for all release builds
but this was causing issues and got reverted in
https://gn-review.googlesource.com/2120, but LTO still makes sense
for release builds where we control the compiler, so we make it an
option which can be enabled as needed.

Change-Id: I4650210a326aeeb00a44d853b8b2da0c90ef17a5
Reviewed-on: https://gn-review.googlesource.com/2200
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Brett Wilson <brettw@chromium.org>
1 file changed
tree: 54d84af9afbf39f4c9ec590481207d18724d1257
  1. base/
  2. build/
  3. infra/
  4. tools/
  5. util/
  6. .clang-format
  7. .editorconfig
  8. .gitignore
  9. .style.yapf
  10. AUTHORS
  11. LICENSE
  12. README.md
README.md

GN

GN is a meta-build system that generates build files for Ninja.

Getting started

git clone https://gn.googlesource.com/gn
cd gn
python build/gen.py
ninja -C out

On Windows, it is expected that cl.exe, link.exe, and lib.exe can be found in PATH, so you'll want to run from a Visual Studio command prompt, or similar.

On Linux and Mac, the default compiler is clang++, a recent version is expected to be found in PATH. This can be overridden by setting CC, CXX, and AR.

Sending patches

GN uses Gerrit for code review. The short version of how to patch is:

... edit code ...
ninja -C out && out/gn_unittests

Then, to upload a change for review:

git commit
git push origin HEAD:refs/for/master  # This uploads for review.

When revising a change, use:

git commit --amend
git push origin HEAD:refs/for/master

which will add the new changes to the existing code review, rather than creating a new one.

TODO: AUTHORS, CLA, etc.