CI: reformat extra long line

Better readability on split screens.

Signed-off-by: Paul Spooren <mail@aparcar.org>

.github/workflows/multi-arch-test-build.yml

@@ -61,7 +61,9 @@ jobs:
       - name: Determine changed packages
         run: |
           # only detect packages with changes
-          PKG_ROOTS=$(find . -name Makefile | grep -v ".*/src/Makefile" | sed -e 's@./\(.*\)/Makefile@\1/@')
+          PKG_ROOTS=$(find . -name Makefile | \
+            grep -v ".*/src/Makefile" | \
+            sed -e 's@./\(.*\)/Makefile@\1/@')
           CHANGES=$(git diff --diff-filter=d --name-only origin/$BRANCH)
 
           for ROOT in $PKG_ROOTS; do