ci: try to fix packed filename for R4 (currently r4lite)

Author: frank-w

.github/workflows/build.yml

@@ -140,7 +140,7 @@ jobs:
 
       - name: Build for bananapi-r4
         run: |
-          sed -ri 's/^#(board=bpi-r4)/\1/' build.conf #change board to r4
+          sed -ri 's/^#(board=bpi-r4)$/\1/' build.conf #change board to r4
           bash build.sh importconfig
           bash build.sh build
       - name: Pack for bananapi-r4