chore(ci): Set FSLDIR in main environment

Author: effigies

.github/workflows/pythonpackage.yml

@@ -69,14 +69,15 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
           mamba-version: "*"
-          channels: ${{ env.FSLCONDA }},conda-forge,defaults
+          channels: ${{ env.FSLCONDA }},conda-forge
           channel-priority: true
       - name: Install FSL
         run: |
           mamba install fsl-avwutils
-          mamba env config vars set FSLDIR="$CONDA_PREFIX" FSLOUTPUTTYPE="NIFTI_GZ"
           # Hack because we're not doing a full FSL install
           echo "6.0.7.9" > $CONDA_PREFIX/etc/fslversion
+      - name: Set FSLDIR
+        run: echo FSLDIR=$CONDA_PREFIX >> $GITHUB_ENV
       - name: Upgrade pip
         run: |
           python -m pip install --upgrade pip