osbase/build/mkimage/osimage: remove initial slash in EFI paths

Many places where these paths are used don't need the initial slash, and
it's easier to add it than to remove it.

Change-Id: Iec189628556c9aa1c022fdd46a2c9fe57692e0aa
Reviewed-on: https://review.monogon.dev/c/monogon/+/4194
Tested-by: Jenkins CI
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
diff --git a/osbase/build/mkimage/osimage/osimage.go b/osbase/build/mkimage/osimage/osimage.go
index 4cd3952..4edb077 100644
--- a/osbase/build/mkimage/osimage/osimage.go
+++ b/osbase/build/mkimage/osimage/osimage.go
@@ -8,7 +8,6 @@
 import (
 	"fmt"
 	"io"
-	"strings"
 
 	"github.com/google/uuid"
 
@@ -32,9 +31,9 @@
 	DataLabel    = "METROPOLIS-NODE-DATA"
 	ESPLabel     = "ESP"
 
-	EFIPayloadPath = "/EFI/BOOT/BOOTx64.EFI"
-	EFIBootAPath   = "/EFI/metropolis/boot-a.efi"
-	EFIBootBPath   = "/EFI/metropolis/boot-b.efi"
+	EFIPayloadPath = "EFI/BOOT/BOOTx64.EFI"
+	EFIBootAPath   = "EFI/metropolis/boot-a.efi"
+	EFIBootBPath   = "EFI/metropolis/boot-b.efi"
 	nodeParamsPath = "metropolis/parameters.pb"
 )
 
@@ -135,7 +134,7 @@
 					PartitionUUID: i.efiPartition.ID,
 				},
 			},
-			efivarfs.FilePath(EFIPayloadPath),
+			efivarfs.FilePath("/" + EFIPayloadPath),
 		},
 	}, nil
 }
@@ -162,11 +161,11 @@
 		return nil, fmt.Errorf("failed to allocate ESP: %w", err)
 	}
 
-	if err := params.efiRoot.PlaceFile(strings.TrimPrefix(EFIBootAPath, "/"), params.EFIPayload); err != nil {
+	if err := params.efiRoot.PlaceFile(EFIBootAPath, params.EFIPayload); err != nil {
 		return nil, err
 	}
 	// Place the A/B loader at the EFI bootloader autodiscovery path.
-	if err := params.efiRoot.PlaceFile(strings.TrimPrefix(EFIPayloadPath, "/"), params.ABLoader); err != nil {
+	if err := params.efiRoot.PlaceFile(EFIPayloadPath, params.ABLoader); err != nil {
 		return nil, err
 	}
 	if params.NodeParameters != nil {