Build linux binaries against sid sysroot

Additionally, this requires building against libstdc++ because there's
no libc++ in the sysroot and we aren't currently set up to build libc++
locally. Because this has broken ChromeOS, use libstdc++ for now and
resolve libc++ build later, if necessary.

Unfortunately this doesn't seem to have changed the readelf -d output,
but hopefully it will help CrOS? I'm not sure.

Before:
[(0c5d936b...)] scottmg@around:/work/gn$ readelf -d out/gn

Dynamic section at offset 0x222270 contains 31 entries:
  Tag        Type                         Name/Value
 0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
 0x0000000000000001 (NEEDED)             Shared library: [ld-linux-x86-64.so.2]
 0x0000000000000001 (NEEDED)             Shared library: [libgcc_s.so.1]
 0x0000000000000001 (NEEDED)             Shared library: [libm.so.6]
 0x0000000000000001 (NEEDED)             Shared library: [libpthread.so.0]
 0x0000000000000001 (NEEDED)             Shared library: [librt.so.1]
 0x0000000000000001 (NEEDED)             Shared library: [libatomic.so.1]

After:
[linux-sysroot] scottmg@around:/work/gn$ readelf -d out/gn

Dynamic section at offset 0x25cc68 contains 31 entries:
  Tag        Type                         Name/Value
 0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
 0x0000000000000001 (NEEDED)             Shared library: [ld-linux-x86-64.so.2]
 0x0000000000000001 (NEEDED)             Shared library: [libgcc_s.so.1]
 0x0000000000000001 (NEEDED)             Shared library: [libm.so.6]
 0x0000000000000001 (NEEDED)             Shared library: [libpthread.so.0]
 0x0000000000000001 (NEEDED)             Shared library: [librt.so.1]
 0x0000000000000001 (NEEDED)             Shared library: [libatomic.so.1]
 ...

Bug: chromium:855791
Change-Id: I1fd8574cdfa5fd856e0fb27d734d15135a00b99a
Reviewed-on: https://gn-review.googlesource.com/1900
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>
2 files changed
tree: 74d1eb01ede0c3abcbd1b3d22bb4f187a9c5da52
  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.