ci: workflows: make tools-buildtest a callable workflow

.github/workflows/tools-buildtest.yml

@@ -1,16 +1,6 @@
 name: tools-buildtest
 
-on:
-  push:
-    branches:
-      - master
-      - staging
-      - trying
-    tags:
-      - '*'
-  pull_request:
-    branches:
-      - '*'
+on: [workflow_call]
 
 jobs:
   tools-build:
@@ -58,10 +48,3 @@ jobs:
       uses: aabadie/riot-action@main
       with:
         cmd: make -C ${{ matrix.tools.path }}/${{ matrix.tools.name }}
-  tools-build-success:
-    # this is only run if all jobs in tools-build succeeded
-    needs: tools-build
-    runs-on: ubuntu-latest
-    steps:
-    - name: tools-build succeeded
-      run: exit 0