MINIFORGE_HOME incorrectly set for Blacksmith runners

The [onnxruntime-feedstock](https://github.com/conda-forge/onnxruntime-feedstock) has the following section in `conda-forge.yaml`: ```yaml azure: ... settings_win: variables: CONDA_BLD_PATH: C:\bld\ MINIFORGE_HOME: C:\Miniforge ``` I'm not entirely sure how these variables are (or were, given that they are targeting "azure") supposed to be used, but `github-actions.yml.tmpl` at least does not appear to allow configuration of this kind when rendering the `conda-build.yml` workflow. The rendered Windows job looks as follows: ```yaml ... - name: Build on windows ... env: # default value; make it explicit, as it needs to match with artefact # generation below. Not configurable for now, can be revisited later CONDA_BLD_DIR: C:\bld MINIFORGE_HOME: ${{ contains(runner.arch, 'ARM') && 'C' || 'D' }}:\Miniforge ``` At least on the Blacksmith CI [runners](https://github.com/conda-forge/admin-requests?tab=readme-ov-file#larger-runners-for-github-actions), it seems to be causing the build to fail during setup of the build environment ([cf](https://github.com/conda-forge/onnxruntime-feedstock/actions/runs/24410961614/job/71307773850)). I assume that may be due to `D:\` not being available on those runners? Manually editing the file to point to `C:\` "solved" the immediate issue and the build environment was [set up correctly](https://github.com/conda-forge/onnxruntime-feedstock/actions/runs/24413346048/job/71316572899?pr=177). I am unsure if the correct fix for this is on the conda-smithy side or with the Blacksmith runners. I suppose this issue may also be relevant: https://github.com/conda-forge/conda-smithy/issues/2349