Spurious failures related to dep_graph.rbml on the bots

[alexcrichton]

Been seeing a bunch of these recently, gonna link up a few PRs to this to track them all here. @michaelwoerister here thought that this is due to the additions in #33171 which seems plausible to me as a bunch of compilations are now sharing the same incremental directory tmp.

cc @arielb1 (pinged on IRC about this)

[alexcrichton]

Believed to be fixed in #33317