3748 zfs headers should be C++ compatible

@@ -50,18 +50,26 @@
 
 .KEEP_STATE:
 
 all: $(PROG)
 
-$(PROG): $(OBJS)
+$(PROG): $(OBJS) ztest_hdrck.o
         $(LINK.c) -o $(PROG) $(OBJS) $(LDLIBS)
         $(POST_PROCESS)
 
 clean:
+        $(RM) $(OBJS) ztest_hdrck.o
 
 lint:   lint_SRCS
 
 include ../../Makefile.targ
 
+ztest_hdrck.cpp: ../ztest_hdrck.sh
+        ../ztest_hdrck.sh
+
+%.o: %.cpp
+        $(COMPILE.cc) $<
+        $(POST_PROCESS_O)
+
 %.o: ../%.c
         $(COMPILE.c) $<
         $(POST_PROCESS_O)