[glom] configure.ac: Check that we have the pg_config utility.

[Murray Cumming <murrayc src gnome org>]

commit e48c77c2e29af4273370a2f2a46132713542bf1d
Author: Murray Cumming <murrayc murrayc com>
Date:   Sat Dec 14 21:26:16 2013 +0100

    configure.ac: Check that we have the pg_config utility.

 configure.ac |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index dded902..5d6c409 100644
--- a/configure.ac
+++ b/configure.ac
@@ -269,6 +269,11 @@ AC_ARG_WITH([postgres-utils],
 AS_IF([test "x$glom_host_win32" != xyes && test "x$glom_enable_client_only" != xyes],
       [AS_CASE([$POSTGRES_UTILS_PATH], [""|no|yes],
 [
+  # For instance, this is in libpq-dev in Ubuntu:
+  AC_CHECK_PROG([PG_CONFIG], [pg_config], [yes], [no])
+  AS_IF([test "$PG_CONFIG" = no],
+    [AC_MSG_ERROR([The PostgreSQL pg_config utility was not found. Glom needs this to find the other 
PostgreSQL utilities.])])
+
   POSTGRES_UTILS_PATH=`pg_config --bindir 2>&AS_MESSAGE_LOG_FD`
   AS_IF(["$POSTGRES_UTILS_PATH/pg_ctl" --version >/dev/null 2>&AS_MESSAGE_LOG_FD],,
         [AC_MSG_ERROR([[