build: add proper dependencies on gdbus-codgen-generated headers

Without this it was possible that ninja built a target that needs
the generated header before the header was generated

fixes #14

src/meson.build

@@ -58,7 +58,7 @@ fbd_dep = declare_dependency(
 
 executable(
   'feedbackd',
-  sources : 'fbd.c',
+  sources : ['fbd.c', generated_dbus_sources[1]],
   include_directories : fbd_inc,
   dependencies : fbd_dep,
   install : true,

tests/meson.build

@@ -71,7 +71,7 @@ fbd_tests = [
 
 foreach test : fbd_tests
   t = executable('test-@0@'.format(test),
-                 ['test-@0@.c'.format(test)],
+                 ['test-@0@.c'.format(test), generated_dbus_sources[1]],
                  c_args : test_fbd_cflags,
                  pie : true,
                  link_args : test_fbd_link_args,