Proper support for ETW on ARM will require additional changes in Go to support
more than 16 bytes of arguments to a syscall callback. Until this work is done,
the ETW package is being changed to no-op on ARM.
There is a cleanup function deferred to remove the provider from the global
provider map. However, this function didn't bind the value of provider ahead of
time, so when the provider creation returned with nil for provider, we tried to
cleanup a nil provider, and panicked.