psu: Add command line argument for JSON config file

Allow for a -c/--config argument to pass in full path to a JSON
configuration file. This argument is optional, if not specified, load
the JSON configuration file from:
/etc/phosphor-psu-monitor/psu_config.json.

Change-Id: I94856c23b09eff32039a1cd26ff35f6f354ea3d4
Signed-off-by: Brandon Wyman <bjwyman@gmail.com>
diff --git a/phosphor-power-supply/meson.build b/phosphor-power-supply/meson.build
index 99e43b0..1bb79de 100644
--- a/phosphor-power-supply/meson.build
+++ b/phosphor-power-supply/meson.build
@@ -2,4 +2,7 @@
 executable(
     'phosphor-psu-monitor',
     'main.cpp',
+    dependencies: [
+        sdbusplus,
+    ],
     install: true)