Harbormaster can send a request in url encoded form while buildkite
expects a POST request with json. Instead of modifying harbormastar or
buildkite this adds a simple proxy that accepts url encoded form and
creates a request that buildkite expects. To avoid potential abuse,
nginx asks for simple http auth credentials stored in harbormaster.
All build parameters passed by proxy are put into build metadata and as
ph_* env variables available during the build.
Secrets involved:
- harbormastert knows http-auth to proxy (stored in privatly and in k8
buildkite/http-auth as auth file);
- proxy knows buildkite api token (mine atm);
- build agent knows conduit API token (mine atm),
and SSH key of llvm-premerge-tests-bot (in k8 buildkite/github-ssh).
Sample build: https://reviews.llvm.org/harbormaster/build/64828/8/https://buildkite.com/llvm-project/premerge/builds/48
