x/build: git http-backend on linux-loong64-3a5000 fails with GIT_PROJECT_ROOT is set but PATH_INFO is not

[bcmills]

The linux-loong64-3a5000 builder started failing as of https://go.dev/cl/491659.
https://build.golang.org/log/2c3437d386796f3252381ab1d3ed9051681bf513:

# get http://127.0.0.1:34721/git/gitrepo1
fatal: GIT_PROJECT_ROOT is set but PATH_INFO is not
# get http://127.0.0.1:34721/git/gitrepo1: 500 Internal Server Error (0.052s)

The HTTP handler is run using a net/http/cgi.Handler via cmd/go/internal/vcweb:
https://cs.opensource.google/go/go/+/master:src/cmd/go/internal/vcweb/git.go;l=40-49;drc=57f9ed5f12ba395fa55880305bc11e1db840f36c

The cgi.Handler unconditionally sets PATH_INFO:
https://cs.opensource.google/go/go/+/master:src/net/http/cgi/host.go;l=118-147;drc=ffa663c9b3c942cbde590bb792179dcca52224b7

So this looks like a bug on loong64 where either that environment variable is not being passed to the git command correctly, or the git command is not reading it correctly.

(attn @golang/loong64)

[gopherbot]

Change https://go.dev/cl/492716 mentions this issue: cmd/go/internal/modfetch/codehost: skip repo tests on linux-loong64-3a5000

[abner-chenc]

Sorry, this error is because the environment variable is set on the builder of loong64 “http_proxy” caused it, I'll deal with it right away.

[bcmills]

Looks like this is now fixed?