use protoc v3.9.0-rc1 for PHP (#655)
use protoc v3.9.0-rc1 for PHP (#655)

* use protoc v3.9.0-rc1 for PHP

Ads ask to try using `protoc` v3.9.0-rc1 for PHP (download location is [here](https://github.com/protocolbuffers/protobuf/releases/download/v3.9.0-rc1/protoc-3.9.0-rc-1-linux-x86_64.zip)). Internal bug ID: 131809012.

* some URLs are weird

googleapis/artman,googleapis/artman,googleapis/artman