bootloader: remove dangling grubenv links

The rhel8.2 .qcow2 images have moved from a single xfs partition into
an EFI style layout with separate /boot/efi partition.

This means the root partition has /boot/grub2/grubenv as a symlink to
../efi/EFI/redhat/grubenv, which is dangling when we are running the
bootloader element as /boot/efi is blank.  grub-install tries to call
rename() in the process of re-writing this file, which fails and bails
out dib.

Remove this symlink if it exists

Change-Id: I5591144a3617dbae148b0c5d2a6a404942ffcd4e
Parital-Bug: #1893029
Redhat-Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1871669

diskimage_builder/elements/bootloader/finalise.d/50-bootloader

@@ -88,6 +88,17 @@ function install_grub2 {
 
     echo "Installing GRUB2..."
 
+    # When using EFI image-based builds, particularly rhel element
+    # based on RHEL>=8.2 .qcow2, we might have /boot/grub2/grubenv
+    # as a dangling symlink to /boot/efi because we have extracted
+    # it from the root fs, but we didn't populate the separate EFI
+    # boot partition from the image.  grub2-install calls rename()
+    # on this file, so if it's a dangling symlink it errors.  Just
+    # remove it if it exists.
+    if [[ -L /boot/grub2/grubenv ]]; then
+        rm -f /boot/grub2/grubenv
+    fi
+
     # We need --force so grub does not fail due to being installed on the
     # root partition of a block device.
     GRUB_OPTS=${GRUB_OPTS:-"--force"}