[gnome-builder] build: Fix configure --with-channel argument help text

[Christian Hergert <chergert src gnome org>]

commit 3895bfebda59c4e23a5e98c9af17d414098073cf
Author: Mart Raudsepp <leio gentoo org>
Date:   Tue Apr 18 14:28:33 2017 +0300

    build: Fix configure --with-channel argument help text

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 194fd7d..4dc55a2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -108,7 +108,7 @@ channel_guess=distro
 AS_IF([test -d "${srcdir}/.git"],[channel_guess=devel])
 AS_IF([test x$UNDER_JHBUILD != x],[channel_guess=jhbuild])
 AC_ARG_WITH([channel],
-            AS_HELP_STRING([--enable-channel=@<:@devel/distro/jhbuild/flatpak-nightly/flatpak-stable@:>@],
+            AS_HELP_STRING([--with-channel=@<:@devel/distro/jhbuild/flatpak-nightly/flatpak-stable@:>@],
                            [Sets the distribution channel for the build to help developers track down bugs]),
             [channel=$withval],
            [channel=$channel_guess])