add note for iar workflow

Author: hathach

.github/workflows/build_iar.yml

@@ -29,6 +29,8 @@ jobs:
       matrix:
         family:
         # Alphabetical order
+        # Note: bundle multiple families into a matrix since there is only one self-hosted instance can
+        # run IAR build. Too many matrix can hurt due to setup/teardown overhead. 
         - 'stm32f0 stm32f1 stm32f4 stm32f7 stm32g4 stm32h7 stm32l4'
     steps:
     - name: Clean workspace
@@ -45,11 +47,11 @@ jobs:
         git submodule update --init lib/FreeRTOS-Kernel lib/lwip lib/sct_neopixel
         python3 tools/get_dependencies.py ${{ matrix.family }}
 
-    - name: Checkout pico-sdk for rp2040
-      if: matrix.family == 'rp2040'
-      run: |
-        git clone --depth 1 -b develop https://github.com/raspberrypi/pico-sdk ~/pico-sdk
-        echo >> $GITHUB_ENV PICO_SDK_PATH=~/pico-sdk
+    #- name: Checkout pico-sdk for rp2040
+    #  if: matrix.family == 'rp2040'
+    #  run: |
+    #    git clone --depth 1 -b develop https://github.com/raspberrypi/pico-sdk ~/pico-sdk
+    #    echo >> $GITHUB_ENV PICO_SDK_PATH=~/pico-sdk
 
     - name: Build
       run: python3 tools/build_family.py ${{ matrix.family }} CC=iccarm