Update emscripten.yml

Author: mcbarton

.github/workflows/emscripten.yml

@@ -671,6 +671,7 @@ jobs:
         emmake make -j ${{ env.ncpus }} install
 
     - name: Test xeus-cpp C++ Emscripten
+      if: ${{ runner.os != 'windows' }}
       shell: bash -l {0}
       run: |
         set -e