tree 874f5ba577ce1652a4d15c4a66ad51c8b7d48b05
parent d6470abef1ca76c40e6da3b4445b7c32f1d0e2e3
author Mitch Rudominer <rudominer@chromium.org> 1496473603 -0700
committer Mitch Rudominer <rudominer@chromium.org> 1497053109 -0700

Adds BUILD.gn file for protobufs.

This is a first cut of the BUILD.gn file. So far I have protoc
compiling successfully. I have not yet tried to use protoc
and so this may change in a later CL.

I haven't yet created a target that uses a compiled_action() to
trigger the build of protoc. For now I have created a target called
"protoc_host_build" that invokes the "protoc" target and
specifies the host toolchain. We may chose to remove this later.

I found I needed to edit a C++ file that is used during the build.
The file embed.cc generates a C++ file called
"well_known_types_embed.cc" that is used by protoc when generating
.js files. But embed.cc writes its generated output to std::cout
and the bazel file redirects std out to "well_known_types_embed.cc".
Wheras the Bazel file used a "genrule" I used a "compiled_action".
But compiled_action doesn't offer a way to redirect the std out from
the process being invoked so instead I changed the process to take
a flag specifying the output.

Change-Id: I21b07564ac1bbdaa4286e787debd003cc9f53917