This installs a upb's static library, headers, and three protoc plugin binaries (upb, upbdefs, upb_minitable). These will now be enabled by default, but can be disabled by setting protobuf_BUILD_LIBUPB=OFF.
To qualify this, we hook into our existing install test infrastructure which attempts to build and run our tests without any of the installation artifacts available from the source tree. Public headers are deleted, and builds of exported libraries/binaries are disabled.
PiperOrigin-RevId: 617376961
Mike Kruskal