cve-check.bbclass: Mitigate symlink related error

cve-check.bbclass: Mitigate symlink related error

According to Yocto reference manual, in description of the
IMAGE_LINK_NAME variable, it is said that

  It is possible to set this to "" to disable symlink creation,
  however, you also need to set :term:`IMAGE_NAME` to still have
  a reasonable value e.g.::

    IMAGE_LINK_NAME = ""
    IMAGE_NAME = "${IMAGE_BASENAME}${IMAGE_MACHINE_SUFFIX}${IMAGE_VERSION_SUFFIX}"

However, when using following additions in local.conf file:

  INHERIT += "cve-check"
  IMAGE_LINK_NAME = ""
  IMAGE_NAME = "${IMAGE_BASENAME}${IMAGE_MACHINE_SUFFIX}${IMAGE_VERSION_SUFFIX}"

the implicit symlink creation in cve_check_write_rootfs_manifest leads
to following build failure

  $ bitbake core-image-minimal core-image-base
  ...
  ERROR: core-image-base-1.0-r0 do_image_complete: Recipe core-image-base is trying to install files into a shared area when those files already exist. The files and the manifests listing them are:
    /home/poky/build/tmp/deploy/images/qemux86-64/.json
      (matched in manifest-qemux86_64-core-image-minimal.image_complete)
  Please adjust the recipes so only one recipe provides a given file.

Mitigate the issue by creating the symlink only in case IMAGE_LINK_NAME
has not been set to empty string.

Signed-off-by: Niko Mauno <niko.mauno@vaisala.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>