unit-test: add nlohmann symlink
unit-test: add nlohmann symlink

Many nlohmann json using packages incorrectly include json.hpp instead
of the fully resolved nlohmann/json.hpp.  OE works around this by
dropping a symlink in include...we'll do the same.

Change-Id: Ic0e266b5ff2e8debff41fc3ba40a31f0e9feafd2
Signed-off-by: Brad Bishop <713d098c0be4c8fd2bf36a94cd08699466677ecd@fuzziesquirrel.com>

openbmc/openbmc-build-scripts,openbmc/openbmc-build-scripts