Ignore pkgrel in kernel rebuild check

A stock kernel packaging-only bump doesn't require rebuilding the
custom kernel.

update-notify

@@ -104,8 +104,9 @@ for stock_pkg in "${!KERNELS[@]}"; do
     fi
 
     # Flag the kernel while the stock one is newer than the newest custom build
-    # (installed, or already built into your repo but not yet installed)
-    if (( $(vercmp "$stock_ver" "$custom_ver") > 0 )); then
+    # (installed, or already built into your repo but not yet installed).
+    # pkgrel is ignored: a stock packaging-only bump doesn't need a rebuild.
+    if (( $(vercmp "${stock_ver%-*}" "${custom_ver%-*}") > 0 )); then
         kernel_lines+=("Rebuild $custom_pkg ($stock_pkg $stock_ver)")
     fi
 done