Add build option to third_party/http2. No functional change. I fixed build complains under http2/. However, adding the build rule in BUILD will require change files we don't own. This build failure is an example when adding build rule to BUILD: http://sponge2/26d093f0-c749-4709-b47d-4ba0646407a1. PiperOrigin-RevId: 324931975 Change-Id: I9296361aaf97cbf36322a52cc017f33185859aa4