Scanning directory on other drive fails on Windows

[lesiw]

GitHub Actions run

Relevant error:

+ go run github.com/bobg/mingo/cmd/mingo@latest -check
go: downloading github.com/bobg/mingo v0.11.1
go: downloading github.com/bobg/errors v1.1.0
go: downloading github.com/bobg/go-generics/v3 v3.7.0
go: downloading golang.org/x/mod v0.20.0
go: downloading golang.org/x/tools v0.24.0
go: downloading golang.org/x/sync v0.8.0
Error: Error scanning directory: scanning package lesiw.io/defers: checking whether D:\a\defers\defers\defers.go is in GOCACHE: computing relative path from C:\Users\runneradmin\AppData\Local to D:\a\defers\defers\defers.go: Rel: can't make D:\a\defers\defers\defers.go relative to C:\Users\runneradmin\AppData\Local

This seems to be because filepath.Rel cannot cross Windows drives.