entity-manager: Search sysconfdir for configurations

Make it easier to iteratively develop configurations in-place with a
read-only /usr.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Id0853b579a61394cb2b6ef0a3858ba01e5cb2893
diff --git a/src/meson.build b/src/meson.build
index 5add400..d1112cc 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -1,4 +1,5 @@
 cpp_args = boost_args + ['-DPACKAGE_DIR="' + packagedir + '/"']
+cpp_args += ['-DSYSCONF_DIR="' + sysconfdir + '/"' ]
 
 executable(
     'entity-manager',