buildRustCrate: remap rustc store path to break rust-src closure leak (#502714)

    (if release then "-C opt-level=3" else "-C debuginfo=2")

    "-C codegen-units=${toString codegenUnits}"

    "--remap-path-prefix=$NIX_BUILD_TOP=/"

    # When the rust-src component is present (common with rust-overlay

    # toolchains), rustc unvirtualises libstd source paths. Panic

    # locations from monomorphised generic std code then embed the

    # toolchain store path in .rodata, pulling the entire toolchain into

    # the closure. Remap to a stable placeholder to break the reference.

    "--remap-path-prefix=${rustc}=/rustc"

    (mkRustcDepArgs dependencies crateRenames)

    (mkRustcFeatureArgs crateFeatures)

  ]