Subiquity crash on Lenovo X13s because UEFI variables not supported

The following crash occurs in curtin.
The device does not provide access to UEFI variables at runtime.

The error from efibootmgr should only result in a warning and not stop the installation process.

         finish: cmd-install/stage-curthooks/builtin/cmd-curthooks/install-grub: FAIL: installing grub to target devices
         finish: cmd-install/stage-curthooks/builtin/cmd-curthooks/configuring-bootloader: FAIL: configuring target system bootloader
         finish: cmd-install/stage-curthooks/builtin/cmd-curthooks: FAIL: curtin command curthooks
         Traceback (most recent call last):
           File "/snap/subiquity/4236/lib/python3.8/site-packages/curtin/commands/main.py", line 202, in main
             ret = args.func(args)
           File "/snap/subiquity/4236/lib/python3.8/site-packages/curtin/commands/curthooks.py", line 1903, in curthooks
             builtin_curthooks(cfg, target, state)
           File "/snap/subiquity/4236/lib/python3.8/site-packages/curtin/commands/curthooks.py", line 1868, in builtin_curthooks
             setup_grub(cfg, target, osfamily=osfamily,
           File "/snap/subiquity/4236/lib/python3.8/site-packages/curtin/commands/curthooks.py", line 818, in setup_grub
             efi_orig_output = util.get_efibootmgr(target)
           File "/snap/subiquity/4236/lib/python3.8/site-packages/curtin/util.py", line 967, in get_efibootmgr
             stdout, _ = in_chroot.subp(['efibootmgr', '-v'], capture=True)
           File "/snap/subiquity/4236/lib/python3.8/site-packages/curtin/util.py", line 787, in subp
             return subp(*args, **kwargs)
           File "/snap/subiquity/4236/lib/python3.8/site-packages/curtin/util.py", line 275, in subp
             return _subp(*args, **kwargs)
           File "/snap/subiquity/4236/lib/python3.8/site-packages/curtin/util.py", line 139, in _subp
             raise ProcessExecutionError(stdout=out, stderr=err,
         curtin.util.ProcessExecutionError: Unexpected error while running command.
         Command: ['unshare', '--fork', '--pid', '--', 'chroot', '/target', 'efibootmgr', '-v']
         Exit code: 2
         Reason: -
         Stdout: ''
         Stderr: EFI variables are not supported on this system.

         Unexpected error while running command.
         Command: ['unshare', '--fork', '--pid', '--', 'chroot', '/target', 'efibootmgr', '-v']
         Exit code: 2
         Reason: -
         Stdout: ''
         Stderr: EFI variables are not supported on this system.