Bug: https://bugs.gentoo.org/782553

--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -663,7 +663,7 @@ clean::
 	$(RM) $(CLEANSUFFIXES:%=libavfilter/dnn/%) $(CLEANSUFFIXES:%=libavfilter/opencl/%) \
               $(CLEANSUFFIXES:%=libavfilter/vulkan/%)
 
-OPENCL = $(subst $(SRC_PATH)/,,$(wildcard $(SRC_PATH)/libavfilter/opencl/*.cl))
+OPENCL = $(wildcard libavfilter/opencl/*.cl)
 .SECONDARY: $(OPENCL:.cl=.c)
 libavfilter/opencl/%.c: TAG = OPENCL
 libavfilter/opencl/%.c: $(SRC_PATH)/libavfilter/opencl/%.cl