osbase/build: update progress messages to contain output short_name

Change-Id: Id41a05a7b8f5cec6e50d9c74ee09309d1a4b504f
Reviewed-on: https://review.monogon.dev/c/monogon/+/3691
Tested-by: Jenkins CI
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
diff --git a/osbase/build/efi.bzl b/osbase/build/efi.bzl
index 2f5f363..7488650 100644
--- a/osbase/build/efi.bzl
+++ b/osbase/build/efi.bzl
@@ -55,7 +55,7 @@
     # Run mkpayload.
     ctx.actions.run(
         mnemonic = "GenEFIKernelImage",
-        progress_message = "Generating EFI unified kernel image",
+        progress_message = "Generating EFI unified kernel image: {}".format(image.short_path),
         inputs = inputs,
         outputs = [image],
         executable = ctx.file._mkpayload,