[gtk-doc] gtk-doc.make: conditionally append to EXTRA_DIST

[Stefan Kost <stefkost src gnome org>]

commit 9a85eb5eee31a5d0171ab6fb0a8d00ce758d4b0f
Author: Ryan Lortie <desrt desrt ca>
Date:   Sat Oct 15 11:48:21 2011 -0400

    gtk-doc.make: conditionally append to EXTRA_DIST
    
    If we detect that EXTRA_DIST has already been defined then append to it
    rather then overwriting it.

 gtk-doc.make        |    6 +++++-
 gtk-doc.notmpl.make |    6 +++++-
 2 files changed, 10 insertions(+), 2 deletions(-)
---
diff --git a/gtk-doc.make b/gtk-doc.make
index 1f75dfd..33c7751 100644
--- a/gtk-doc.make
+++ b/gtk-doc.make
@@ -29,7 +29,11 @@ SETUP_FILES = \
 	$(DOC_MODULE)-sections.txt	\
 	$(DOC_MODULE)-overrides.txt
 
-EXTRA_DIST = 				\
+ifeq ($(origin EXTRA_DIST), undefined)
+EXTRA_DIST =
+end
+
+EXTRA_DIST += 				\
 	$(HTML_IMAGES)			\
 	$(SETUP_FILES)
 
diff --git a/gtk-doc.notmpl.make b/gtk-doc.notmpl.make
index 9841de4..cfdeb86 100644
--- a/gtk-doc.notmpl.make
+++ b/gtk-doc.notmpl.make
@@ -29,7 +29,11 @@ SETUP_FILES = \
 	$(DOC_MODULE)-sections.txt	\
 	$(DOC_MODULE)-overrides.txt
 
-EXTRA_DIST = 				\
+ifeq ($(origin EXTRA_DIST), undefined)
+EXTRA_DIST =
+end
+
+EXTRA_DIST +=				\
 	$(HTML_IMAGES)			\
 	$(SETUP_FILES)