[sdk][tools] Strip host tools that are included in the SDK

This reduces the size of tools shipped in the SDK, especially
substantially for zxdb.

This strips garnet C++ tools (far, zxdb) and Go-built ones (amber-srv,
amber-publish, pm, ...), but not Zircon tools yet (fidlc, fidl-format,
...).

DX-555 #comment

Test: Manually build SDK for Chromium and confirm size of binaries in tools/
Change-Id: I3a87bf0e4c27704b0f0f89da484b100e76bd5eae
2 files changed