classes/license: fix handling of symlinks pointed to in LIC_FILES_CHKSUM
If you set LIC_FILES_CHKSUM to point to a relative symlink then you'll
get "Could not copy license file" warnings in copy_license_files() since
the symlink won't be valid after it's copied. If the source is a symlink
then we need to dereference it first.
I encountered this when I used recipetool on the sources for capnproto,
where the c++ directory contains a LICENSE.txt symlink to the LICENSE
file in the parent directory, and this symlink ends up being pointed to
in LIC_FILES_CHKSUM.
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
