Let flagpoll find packages in the MacPorts prefix.
https://github.com/mccdo/flagpoll/issues/7
--- flagpoll.orig	2010-09-05 11:43:01.000000000 -0500
+++ flagpoll	2023-03-08 23:21:26.000000000 -0600
@@ -240,7 +240,7 @@
       path_list.extend(flg_cfg_dir)
       path_list.extend(pkg_cfg_dir)
       path_list.extend(ld_path)
-      default_path_list = [pj('/','usr','lib64'), pj('/','usr','lib32'), pj('/','usr','lib'), pj('/','usr','share')]
+      default_path_list = ['@PREFIX@/lib', '@PREFIX@/share', pj('/','usr','lib64'), pj('/','usr','lib32'), pj('/','usr','lib'), pj('/','usr','share')]
       default_path_pkg = [pj(p,'pkgconfig') for p in default_path_list]
       default_path_flg = [pj(p,'flagpoll') for p in default_path_list]
       path_list.extend(default_path_pkg)