To fix undefined errors like to_float. This tool is often not built as
LLVM_ENABLE_HTTPLIB defaults to off (and the external dependency
cpp-httplib is difficult to set up due to a dependency on brotli) and
LLVM_TOOL_LLVM_DEBUGINFOD_BUILD disabling logic in D147185.
This implements a debuginfod server in llvm using the `DebuginfodCollection` and `DebuginfodServer` classes. This is tested with lit tests against the debuginfod-find client.
The server scans 0 or more local directories for artifacts. It serves the debuginfod protocol over HTTP. Only the `executable` and `debuginfo` endpoints are supported (no `/source` endpoint).
The server also uses the debuginfod client as a fallback, so it can hit the local debuginfod cache or federate to other known debuginfod servers.
The client behavior is controllable through the standard environment variables (`DEBUGINFOD_URLS`, `DEBUGINFOD_CACHE_PATH`, `DEBUGINFOD_TIMEOUT`)
The server implements on-demand collection updates as follows:
If the build-id is not found by a local lookup, rescan immediately and look up the build-id again before returning 404. To protect against DoS attacks, do not rescan more frequently than once per N seconds (specified by `-m`).
Lit tests are provided which test the `llvm-debuginfod-find` client against the `llvm-debuginfod` server.
Reviewed By: mysterymath
Differential Revision: https://reviews.llvm.org/D114846
