Binary distribution build on Windows fails

It appears that the reloc-binary-dist target is broken in at least some situations on Windows. Specifically, the configure invocation performed by Rules.BinaryDist.installTo fails to find the in-place mingw toolchain, causing ghc-toolchain to conclude that there is no valid object merging tool available:

[Error {errorMessage = "Neither a object-merging tool (e.g. ld -r) nor an ar that supports -L is available", errorLogContexts = []}]

What is perplexing is that this appears to work in CI: the build system manages to produce a binary distribution, albeit a broken one for unrelated reasons (#24525 (closed)).