Use pg_config to determine include and lib dirs

Setup.hs

@@ -1,2 +1,51 @@
+#!/usr/bin/env runhaskell
+
 import Distribution.Simple
-main = defaultMain
+import Distribution.PackageDescription
+import Distribution.Version
+
+import Distribution.Simple.LocalBuildInfo
+import Distribution.Simple.Program
+import Distribution.Verbosity
+
+import Data.Char (isSpace)
+import Data.List (dropWhile,reverse)
+
+import Control.Monad
+
+main = defaultMainWithHooks simpleUserHooks {
+  hookedPrograms = [pgconfigProgram],
+
+  confHook = \pkg flags -> do
+    lbi <- confHook simpleUserHooks pkg flags
+    bi <- psqlBuildInfo lbi
+
+    return lbi {
+      localPkgDescr = updatePackageDescription
+                        (Just bi, [("runtests", bi)]) (localPkgDescr lbi)
+    }
+}
+
+pgconfigProgram = (simpleProgram "pgconfig") {
+    programFindLocation = \verbosity -> do
+      pgconfig  <- findProgramLocation verbosity "pgconfig"
+      pg_config <- findProgramLocation verbosity "pg_config"
+      return (pgconfig `mplus` pg_config)
+  }
+
+psqlBuildInfo :: LocalBuildInfo -> IO BuildInfo
+psqlBuildInfo lbi = do
+  (pgconfigProg, _) <- requireProgram verbosity
+                         pgconfigProgram (withPrograms lbi)
+  let pgconfig = rawSystemProgramStdout verbosity pgconfigProg
+
+  incDir <- pgconfig ["--includedir"]
+  libDir <- pgconfig ["--libdir"]
+
+  return emptyBuildInfo {
+    extraLibDirs = [strip libDir],
+    includeDirs  = [strip incDir]
+  }
+  where
+    verbosity = normal -- honestly, this is a hack
+    strip x = dropWhile isSpace $ reverse $ dropWhile isSpace $ reverse x

libpq.cabal

@@ -16,9 +16,9 @@ Author:              Grant Monroe
 Maintainer:          grant@tnarg.com
 -- Copyright:
 Category:            Database
-Build-type:          Simple
+Build-type:          Custom
 -- Extra-source-files:
-Cabal-version:       >=1.2
+Cabal-version:       >=1.8
 Library
   Exposed-modules:     Database.PQ