chore: add Makevars

src/Makevars

@@ -0,0 +1,11 @@
+SOURCES = tinyxml2.cpp calsht.cpp shoupai.cpp \
+  shan.cpp he.cpp hule.cpp svg.cpp \
+  feature.cpp xiangting.cpp \
+  random.cpp skksph.cpp RcppExports.cpp
+
+OBJ = $(SOURCES:.cpp=.o)
+OBJECTS = $(OBJ:.cpp=.o)
+
+all: $(SHLIB)
+
+clean: rm -f $(SHLIB) $(OBJECTS)