Fix license in package.xml for SPDX conformance

[eigendude]

Description

This PR updates the <license> tag in package.xml to BSD-2-Clause. It fixes building this package for Yocto after it started requiring SPDX license IDs.

Motivation and Context

Required to build Yocto images with the apriltag package (tested with version 3.4.3).

Related PRs

Yocto SDPX discussion in the meta-ros Yocto meta-layer:

• scarthgap: license issue in build time ros/meta-ros#1208
• [scarthgap] License issues checking by SPDX License. ros/meta-ros#1216

How has this been tested?

Before, Yocto builds fail when including the apriltag package with the error:

WARNING: apriltag-3.4.3-2-r0 do_populate_lic: QA Issue: apriltag: No generic license file exists for: BSD in any provider [license-exists]
ERROR: apriltag-3.4.3-2-r0 do_create_spdx: Cannot find any text for license BSD

When I manually update the license to BSD-2-Clause (and also apply ros/meta-ros#1660), the Yocto build succeeds:

diff --git a/recipes-ros/apriltag/apriltag_%.bbappend b/recipes-ros/apriltag/apriltag_%.bbappend
new file mode 100644
index 0000000..ed4ad0c
--- /dev/null
+++ b/recipes-ros/apriltag/apriltag_%.bbappend
@@ -0,0 +1 @@
+LICENSE = "BSD-2-Clause"

[christian-rauch]

Makes sense. For reference, the full licence name (BSD 2-Clause License) is specified here:

apriltag/LICENSE.md

Line 1 in c5a4fc1

BSD 2-Clause License