as when using -buildmode=c-archive, we know that Go runtime
initialization is complete but we do not know that all Go init
functions have been run. We should not fetch cgo_context_function
until they have been, because that is where a call to
SetCgoTraceback is likely to occur. We are going to wait for Go
initialization to be complete anyhow, later, by waiting for
main_init_done to be closed in cgocallbackg1. We should wait here
instead. See also issue golang#15943.