ci.yml: Make sure PATH persists between steps

Source of fix: https://github.com/spinalcordtoolbox/spinalcordtoolbox/blob/a902e199c23d4e95d5a050dcd5ad4ebccdb0e279/.github/workflows/create-release.yml#L98-L103

.github/workflows/ci.yml

@@ -41,7 +41,11 @@ jobs:
           git clone https://github.com/spinalcordtoolbox/spinalcordtoolbox.git
           cd spinalcordtoolbox
           ./.ci.sh -i
-          export PATH="$PWD/spinalcordtoolbox/bin:$PATH"
+          # NB: install_sct edits ~/.bashrc, but those environment changes don't get passed to subsequent steps in GH Actions.
+          # So, we filter through the .bashrc and pass the values to $GITHUB_ENV and $GITHUB_PATH.
+          # Relevant documentation: https://docs.github.com/en/actions/reference/workflow-commands-for-github-actions#environment-files
+          cat ~/.bashrc | grep "export SCT_DIR" | cut -d " " -f 2 >> $GITHUB_ENV
+          cat ~/.bashrc | grep "export PATH" | grep -o "/.*" | cut -d ':' -f 1 >> $GITHUB_PATH
 
       - name: Run tests with pytest
         run: |