[libgdata] build: Use AM_DISTCHECK_CONFIGURE_FLAGS not DISTCHECK_CONFIGURE_FLAGS

[Philip Withnall <pwithnall src gnome org>]

commit e806dea38f5807475e7b28e0d27b633e61fd35fa
Author: Philip Withnall <withnall endlessm com>
Date:   Tue Oct 17 12:16:52 2017 +0100

    build: Use AM_DISTCHECK_CONFIGURE_FLAGS not DISTCHECK_CONFIGURE_FLAGS
    
    The former is for the build system to use; the latter is for the user to
    override what the build system says.
    
    See
    https://www.gnu.org/software/automake/manual/html_node/Checking-the-Distribution.html.
    
    Signed-off-by: Philip Withnall <withnall endlessm com>

 Makefile.am |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 044193c..858fb7f 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -2,7 +2,7 @@ SUBDIRS = . po docs gdata/tests
 
 ACLOCAL_AMFLAGS = --install -I m4 ${ACLOCAL_FLAGS}
 
-DISTCHECK_CONFIGURE_FLAGS =
+AM_DISTCHECK_CONFIGURE_FLAGS =
 MAINTAINERCLEANFILES =
 
 CLEANFILES =
@@ -570,7 +570,7 @@ check-headers:
 INTROSPECTION_GIRS =
 INTROSPECTION_SCANNER_ARGS = --warn-all
 INTROSPECTION_COMPILER_ARGS =
-DISTCHECK_CONFIGURE_FLAGS += --enable-introspection
+AM_DISTCHECK_CONFIGURE_FLAGS += --enable-introspection
 EXTRA_DIST += m4/introspection.m4
 
 if HAVE_INTROSPECTION
@@ -857,7 +857,7 @@ MAINTAINERCLEANFILES += \
        m4/intltool.m4 \
        $(NULL)
 
-DISTCHECK_CONFIGURE_FLAGS += --enable-gtk-doc
+AM_DISTCHECK_CONFIGURE_FLAGS += --enable-gtk-doc
 
 # pkgconfig data
 pkgconfigdir = $(libdir)/pkgconfig