[gnome-user-share] build: Fix syntax error introduced in 05df084

[Bastien Nocera <hadess src gnome org>]

commit 792d69097438147969d225991f9a7f762c02539b
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Wed Aug 31 14:37:43 2016 +0300

    build: Fix syntax error introduced in 05df084
    
    See https://bugzilla.gnome.org/show_bug.cgi?id=766330

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index c598fe5..f31ed41 100644
--- a/configure.ac
+++ b/configure.ac
@@ -99,7 +99,7 @@ AM_GLIB_GNU_GETTEXT
 
 dnl ==========================================================================
 dnl systemd user unit directory
-PKG_CHECK_EXISTS (systemd,, AC_MSG_ERROR ([systemd development headers not found]))
+PKG_CHECK_EXISTS([systemd],, [AC_MSG_ERROR([systemd development headers not found])])
 AC_ARG_WITH([systemduserunitdir],
            AS_HELP_STRING([--with-systemduserunitdir=DIR], [Directory for systemd user service files]),
            [],