Add ANGLE VK repo build overrides

Updating ANGLE to use integrated BUILD.gn files from the Vulkan Loader,
Headers, Tools, and ValidationLayers repos. Need to add these build
overrides files to Chromium as well.

Bug: angleproject:3320
Change-Id: I4306f3383f06eb4a79d4331717445621a16a5331
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1610488
Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Tobin Ehlis <tobine@google.com>
Auto-Submit: Tobin Ehlis <tobine@google.com>
Cr-Original-Commit-Position: refs/heads/master@{#663215}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 0b9f739c4e8eeeebf239d59b10830e5d7923901c
4 files changed
tree: 523aa7b79146c74988deaba0d1d13c6332f0e15b
  1. OWNERS
  2. README.md
  3. angle.gni
  4. build.gni
  5. dawn.gni
  6. glslang.gni
  7. gtest.gni
  8. pdfium.gni
  9. shaderc.gni
  10. spirv_tools.gni
  11. vulkan_common.gni
  12. vulkan_loader.gni
  13. vulkan_tools.gni
  14. vulkan_validation_layers.gni
README.md

Build overrides in GN

This directory is used to allow different products to customize settings for repos that are DEPS'ed in or shared.

For example: V8 could be built on its own (in a “standalone” configuration), and it could be built as part of Chromium. V8 might define a top-level target, //v8:d8 (a simple executable), that should only be built in the standalone configuration. To figure out whether or not it should be in a standalone configuration, v8 can create a file, build_overrides/v8.gni, that contains a variable, build_standalone_d8 = true. and import it (as import(“//build_overrides/v8.gni”) from its top-level BUILD.gn file.

Chromium, on the other hand, might not need to build d8, and so it would create its own build_overrides/v8.gni file, and in it set build_standalone_d8 = false.

The two files should define the same set of variables, but the values can vary as appropriate to the needs of the two different builds.

The build.gni file provides a way for projects to override defaults for variables used in //build itself (which we want to be shareable between projects).

TODO(crbug.com/588513): Ideally //build_overrides and, in particular, //build_overrides/build.gni should go away completely in favor of some mechanism that can re-use other required files like //.gn, so that we don't have to keep requiring projects to create a bunch of different files to use GN.