build-unit-test-docker: add cjson for skeleton

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Id70c0c648e53f3c945b953ca1edb63fff152f559
diff --git a/scripts/build-unit-test-docker b/scripts/build-unit-test-docker
index f51af2a..26c2964 100755
--- a/scripts/build-unit-test-docker
+++ b/scripts/build-unit-test-docker
@@ -838,6 +838,7 @@
     libaudit-dev \
     libc6-dbg \
     libc6-dev \
+    libcjson-dev \
     libconfig++-dev \
     libcryptsetup-dev \
     libdbus-1-dev \