Add STATIC_LINKING ifdef

Makefile.libretro

@@ -1,6 +1,7 @@
-DEBUG = 0
-EXTERNAL_ZLIB = 0
-HAVE_GRIFFIN = 1
+DEBUG=0
+EXTERNAL_ZLIB=0
+HAVE_GRIFFIN=1
+STATIC_LINKING=0
 
 ifeq ($(platform),)
 	platform = unix
@@ -280,6 +281,10 @@ OBJECTS := $(SOURCES_C:.c=.o)
 
 DEFINES := -D__LIBRETRO__ -DSOUND_QUALITY=0 -DPATH_MAX=1024 -DINLINE=inline -DPSS_STYLE=1 -DFCEU_VERSION_NUMERIC=9813 -DFRONTEND_SUPPORTS_RGB565 $(PLATFORM_DEFINES)
 
+ifeq ($(STATIC_LINKING),1)
+	DEFINES += -DSTATIC_LINKING
+endif
+
 ifeq ($(platform), sncps3)
 WARNING_DEFINES =
 else

src/drivers/libretro/griffin.c

@@ -1,7 +1,9 @@
 #ifdef WANT_GRIFFIN
 
 #include "drivers/libretro/libretro.c"
+#ifdef STATIC_LINKING
 #include "../../memstream.c"
+#endif
 
 #include "cart.c"
 #include "cheat.c"