Run multi-gcc on develop

Add concurrency to cancel in progress runs on new commits to same branch

.github/workflows/multi-gcc.yml

diff --git a/.github/workflows/multi-gcc.yml b/.github/workflows/multi-gcc.yml
index f200624..a728b13 100644
--- a/.github/workflows/multi-gcc.yml
+++ b/.github/workflows/multi-gcc.yml
@@ -5,8 +5,13 @@
   push:
     branches:
       - 'master'
+      - 'develop'
       - 'test_workflow'
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event_name }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     if: github.repository_owner == 'raspberrypi'