cmd/bent: inherit http_proxy variable

Change-Id: I6d22487c8967cdc92b84a31f622c9d6c3eface1f
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/565635
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

cmd/bent/bent.go

diff --git a/cmd/bent/bent.go b/cmd/bent/bent.go
index 11938cb..f15bc94 100644
--- a/cmd/bent/bent.go
+++ b/cmd/bent/bent.go
@@ -465,6 +465,8 @@
 			defaultEnv = append(defaultEnv, e)
 		}
 	}
+	defaultEnv = inheritEnv(defaultEnv, "http_proxy")
+	defaultEnv = inheritEnv(defaultEnv, "https_proxy")
 	defaultEnv = replaceEnv(defaultEnv, "GOPATH", dirs.gopath)
 	defaultEnv = replaceEnv(defaultEnv, "GOOS", runtime.GOOS)
 	defaultEnv = replaceEnv(defaultEnv, "GOARCH", runtime.GOARCH)