json: use latest to get gcc10 fixes

nlohmann required some changes for gcc10. Those changes have not been
officially released yet by the project.

The following issues has details on the bug:
https://github.com/nlohmann/json/issues/1920

Change-Id: I853f36f961fcd094a3f399028182c308a970c2e5
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/build-unit-test-docker.sh b/build-unit-test-docker.sh
index 7c00c30..380da05 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -100,8 +100,10 @@
   [function2]=3a0746bf5f601dfed05330aefcb6854354fce07d
   # Snapshot from 2020-02-13
   [googletest]=23b2a3b1cf803999fb38175f6e9e038a4495c8a5
-  # Release 2019-11-17
-  [json]=v3.7.3
+  # TODO - Move back to released json once gcc10 fix is available
+  # [json]=v3.7.3
+  # Snapshot from 2020-05-19
+  [json]=5cfa8a586ee1a656190491c1de20a82fb40fab5d
   # Snapshot from 2019-05-24
   [lcov]=75fbae1cfc5027f818a0bb865bf6f96fab3202da
   # dev-5.0 2019-05-03
@@ -304,9 +306,12 @@
 make -j$(nproc) && \
 make install
 
+# nlohmann json provides all of its function in a single header file
+# TODO - Go back to using a release once gcc 10 fixes are in
+# curl -L -o ${PREFIX}/include/nlohmann/json.hpp https://github.com/nlohmann/json/releases/download/${PKG_REV['json']}/json.hpp
 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 ${PREFIX}/include/nlohmann/json.hpp https://raw.githubusercontent.com/nlohmann/json/${PKG_REV['json']}/single_include/nlohmann/json.hpp && \
 ln -s nlohmann/json.hpp ${PREFIX}/include/json.hpp
 
 FROM openbmc-base as openbmc-fifo_map