postgresql: Fix nits after cross fixes

pkgs/development/libraries/libossp-uuid/default.nix

@@ -10,14 +10,12 @@ stdenv.mkDerivation {
     sha256= "11a615225baa5f8bb686824423f50e4427acd3f70d394765bdff32801f0fd5b0";
   };
 
-  configureFlags = stdenv.lib.optional stdenv.isFreeBSD "--with-pic";
+  configureFlags = [
+    "ac_cv_va_copy=yes"
+  ] ++ stdenv.lib.optional stdenv.isFreeBSD "--with-pic";
 
   patches = [ ./shtool.patch ];
 
-  preConfigure = ''
-  export ac_cv_va_copy=yes
-  '';
-
   meta = with stdenv.lib; {
     homepage = http://www.ossp.org/pkg/lib/uuid/;
     description = "OSSP uuid ISO-C and C++ shared library";

pkgs/servers/sql/postgresql/default.nix

@@ -30,9 +30,8 @@ let
       "--sysconfdir=/etc"
       "--libdir=$(lib)/lib"
       "--with-system-tzdata=${tzdata}"
-    ] ++ (
-      if stdenv.isDarwin then [ "--with-uuid=e2fs" ] else [ "--with-ossp-uuid" ]
-    );
+      (if stdenv.isDarwin then "--with-uuid=e2fs" else "--with-ossp-uuid")
+    ];
 
     patches =
       [ (if atLeast "9.4" then ./disable-resolve_symlinks-94.patch else ./disable-resolve_symlinks.patch)