Add associations support to phosphor-inventory-mgr

Add support so another layer can select the 'associations'
PACKAGECONFIG and install their own associations.json file
which the phosphor-inventory code uses to create associations
between inventory paths and other paths.

(From meta-phosphor rev: 6bc9cd4952999bbb8bb5083c1c6e89b6ad2c8b8b)

Change-Id: Id0cb5f5a7f8759455c1ebaa068ab6c810c118f5f
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-phosphor/recipes-phosphor/inventory/phosphor-inventory-manager_git.bb b/meta-phosphor/recipes-phosphor/inventory/phosphor-inventory-manager_git.bb
index c6e3b29..1b54dd5 100644
--- a/meta-phosphor/recipes-phosphor/inventory/phosphor-inventory-manager_git.bb
+++ b/meta-phosphor/recipes-phosphor/inventory/phosphor-inventory-manager_git.bb
@@ -39,3 +39,6 @@
         IFACE=${OBMC_INVENTORY_MGR_IFACE} \
         IFACES_PATH=${STAGING_DIR_NATIVE}${yaml_dir} \
         "
+
+PACKAGECONFIG ??= ""
+PACKAGECONFIG[associations] = "--enable-associations, --disable-associations,nlohmann-json,"