license.bbclass: fix missing of license files on ubuntu build host

license.bbclass: fix missing of license files on ubuntu build host

The license_create_manifest function contains bashism, this will lead
to unexpected results on ubuntu build host, as sh is linked to dash on
ubuntu. Even if COPY_LIC_MANIFEST and COPY_LIC_DIRS are enabled, the
license files will still be missing on target.

This patch fixes the above problem.

[YOCTO #5549]

(From OE-Core rev: 4df9daee5c732c0a20dabe8515577238a1508512)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>