[gnome-control-center] build: Add missing backslashes

[Bastien Nocera <hadess src gnome org>]

commit 4216163744886ee6b83e2d1d8d3d1a58f65382d5
Author: Ting-Wei Lan <lantw src gnome org>
Date:   Thu Aug 6 20:43:16 2015 +0800

    build: Add missing backslashes
    
    https://bugzilla.gnome.org/show_bug.cgi?id=753316

 configure.ac |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 4dccaa5..3d6efbd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -433,9 +433,9 @@ case $host_os in
       # Nothing
       echo "USB-related panels disabled on S390"
     else
-      if test "x$have_networkmanager" != "xyes" -o
-              "x$have_bluetooth" != "xyes" -o
-              "x$enable_cups" != "xyes" -o
+      if test "x$have_networkmanager" != "xyes" -o \
+              "x$have_bluetooth" != "xyes" -o \
+              "x$enable_cups" != "xyes" -o \
               "x$have_wacom" != "xyes"; then
         AC_MSG_ERROR([The Network, Bluetooth, Printers and Wacom panels are not optional on Linux systems])
      fi