Merge changes I980677f3,If2d0d04f,I3bc7a0d5,I1e956ab5,Ic5b62063, ...
* changes:
gn2bp: collect sources for each architecture
gn2bp: add code that collects common sources
gn2bp: get arch from toolchain
gn2bp: remove toolchain label from dependencies
gn2bp: add arch to Target
gn2bp: use name without toolchain for Targets
gn2bp: remove unused third_party deps handling
gn2bp: pass gn_target_name into get_proto_target_type
gn2bp: pass gn_desc to parse_gn_desc
gn2bp: separate parsing gn desc from retrieving Target object
gn2bp: use discard instead of remove
gn2bp: do not build root_store_tool
gn2bp: link libprotobuf statically