ovmf-shell-image.bb: simplify dependencies

The image consists only of the EFI system partition, therefore
we can avoid depending on the default wic tools.

(From OE-Core rev: f147b2502ae53d63a884a46e994ae18e12ec4ef6)

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/ovmf/ovmf-shell-image.bb

@@ -1,10 +1,13 @@
 DESCRIPTION = "boot image with UEFI shell and tools"
 
 # For this image recipe, only the wic format with a
-# single vfat partition makes sense.
+# single vfat partition makes sense. Because we have no
+# boot loader and no rootfs partition, not additional
+# tools are needed for this .wks file.
 IMAGE_FSTYPES_forcevariable = 'wic'
-
 WKS_FILE = "ovmf/ovmf-shell-image.wks"
+WKS_FILE_DEPENDS = ""
+
 inherit image
 
 # We want a minimal image with just ovmf-shell-efi unpacked in it. We