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 <bradleyb@fuzziesquirrel.com>
diff --git a/build-unit-test-docker.sh b/build-unit-test-docker.sh
index a46c1e1..9acca5c 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -300,7 +300,8 @@
 
 FROM openbmc-base as openbmc-json
 RUN mkdir ${PREFIX}/include/nlohmann/ && \
-curl -L -o ${PREFIX}/include/nlohmann/json.hpp https://github.com/nlohmann/json/releases/download/${PKG_REV['json']}/json.hpp
+curl -L -o ${PREFIX}/include/nlohmann/json.hpp https://github.com/nlohmann/json/releases/download/${PKG_REV['json']}/json.hpp && \
+ln -s nlohmann/json.hpp ${PREFIX}/include/json.hpp
 
 FROM openbmc-base as openbmc-span-lite
 RUN curl -L https://github.com/martinmoene/span-lite/archive/${PKG_REV['span-lite']}.tar.gz | tar -xz && \