fuzz-tests: Add a test for fundee_channel()

Changelog-None: `fundee_channel()` in `openingd/openingd.c` is
responsible for handling incoming `open_channel` messages from a
peer. Since it deals with external input, add a test for it.

Author: Chandra Pratap

tests/fuzz/Makefile

@@ -72,5 +72,16 @@ FUZZ_COMMON_OBJS := \
 $(FUZZ_TARGETS_OBJS): $(COMMON_HEADERS) $(WIRE_HEADERS) $(COMMON_SRC)
 $(FUZZ_TARGETS_BIN): $(LIBFUZZ_OBJS) $(FUZZ_COMMON_OBJS) $(BITCOIN_OBJS)
 
+tests/fuzz/fuzz-open_channel:	common/shutdown_scriptpubkey.o		\
+				common/penalty_base.o			\
+				common/read_peer_msg.o			\
+				common/peer_io.o			\
+				common/peer_billboard.o			\
+				common/peer_status_wiregen.o		\
+				common/per_peer_state.o			\
+				openingd/common.o			\
+				openingd/openingd_wiregen.o		\
+				hsmd/hsmd_wiregen.o
+
 ALL_C_SOURCES += $(FUZZ_TARGETS_SRC) $(LIBFUZZ_SRC)
 ALL_FUZZ_TARGETS += $(FUZZ_TARGETS_BIN)