Move //build/module_args/v8.gni to //build_overrides.

build_overrides/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,

[tfarina, 2015/10/13 05:11:49]

Right, I think with this example I can see how this looks like.

v8 in their tree will have to create a build_overrides/ directory and create a
v8.gni.

Then here in our tree (chromium) we will also have a build_overrides that does
what? 'overrides' their variables.

Very clever! :)

If they are fine with having to create this build_overrides/ directory, I don't
know, but who am I, right? I think Henrik was happy at least ;)

[kjellander_chromium, 2015/10/13 07:31:35]

Yeah, I'm happy for the WebRTC use case, since we face similar problems as V8,
being both standalone and a part of Chromium.

+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.