[gtk/uajain/clean-gtktypefuncs] gtk/Makefile: Add generated gtktypefuncs.c to DISTCLEANFILES

[Umang Jain <uajain src gnome org>]

commit adbd9b22d6ef5c1578e7d48b575e3d5fcda519fc
Author: Umang Jain <umang endlessm com>
Date:   Thu Apr 11 11:27:17 2019 +0530

    gtk/Makefile: Add generated gtktypefuncs.c to DISTCLEANFILES
    
    Otherwise, it errors out on make distcleancheck in debian packaging
    
    ```
    ERROR: files left in build directory after distclean:
    ./gtk/gtktypefuncs.c
    make[1]: *** [Makefile:1005: distcleancheck] Error 1
    ```

 gtk/Makefile.am | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gtk/Makefile.am b/gtk/Makefile.am
index e556e9d3af..ea2dd5863c 100644
--- a/gtk/Makefile.am
+++ b/gtk/Makefile.am
@@ -1177,7 +1177,7 @@ MAINTAINERCLEANFILES = \
        $(print_portal_built_sources)           \
        $(stamp_files)
 
-DISTCLEANFILES =
+DISTCLEANFILES = gtktypefuncs.c
 
 if OS_WIN32
 DISTCLEANFILES += gtk-win32.rc