gcc-10 defaults to -fno-common, which exposes a symbol conflict, so
use `static` correctly. Also we don't use `parent_extractable_iface`
in `ges-uri-clip.c`.
See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85678
#define parent_class ges_uri_clip_parent_class
-GESExtractableInterface *parent_extractable_iface;
-
struct _GESUriClipPrivate
{
gchar *uri;
#include "ges-extractable.h"
#define parent_class ges_video_source_parent_class
-GESExtractableInterface *parent_extractable_iface = NULL;
+static GESExtractableInterface *parent_extractable_iface = NULL;
struct _GESVideoSourcePrivate
{