Another (probably better) way added by sjamaan on Sat Apr 28 20:17:05 2012

Index: postgresql.setup
===================================================================
--- postgresql.setup    (revision 26575)
+++ postgresql.setup    (working copy)
@@ -3,8 +3,7 @@
 (use files)
 
 (define libpq-flags
-  `(-C -I -C "\"`pg_config --includedir`\"" -L -L -L "\"`pg_config --libdir`\""
-       -rpath "\"`pg_config --libdir`\"" -lpq))
+  `(-C -I -C "\"`pg_config --includedir`\"" -L "\"`pg_config --ldflags`\"" -lpq))
 
 (define PQescapeIdentifier-presence-checker #<<EOF
   #include <libpq-fe.h>