only set --break-system-packages as environment to be compatible with older versions

.github/workflows/ci.yml

@@ -10,6 +10,8 @@ jobs:
         os: [ubuntu-latest]
     
     runs-on: ${{ matrix.os }}
+    env:
+      PIP_BREAK_SYSTEM_PACKAGES:1
     steps:
       - uses: actions/checkout@v2
         with: 
@@ -17,8 +19,8 @@ jobs:
       - name: Install deps
         run: |
           #apt-get install -y python3-pip
-          python3 -m pip install --upgrade pip --break-system-packages
-          pip install -U platformio --break-system-packages
+          python3 -m pip install --upgrade pip
+          pip install -U platformio
       - name: Build
         run: |
           pio run