add: exercise answer for chapter 6 and 7

exercises/6/Makefile

@@ -0,0 +1,38 @@
+#
+# Makefile
+# web_server
+#
+# created by changkun at labex.io
+#
+
+CXX = g++
+EXEC_HTTP = server.http
+EXEC_HTTPS = server.https
+
+SOURCE_HTTP = main.http.cpp
+SOURCE_HTTPS = main.https.cpp
+
+OBJECTS_HTTP = main.http.o
+OBJECTS_HTTPS =  main.https.o
+
+LDFLAGS_COMMON = -std=c++11 -O3 -pthread -lboost_system
+LDFLAGS_HTTP =
+LDFLAGS_HTTPS = -lssl -lcrypto
+
+LPATH_COMMON = -I/usr/include/boost
+LPATH_HTTP =
+LPATH_HTTPS = -I/usr/include/openssl
+
+LLIB_COMMON = -L/usr/lib
+
+all:
+	make http
+	make https
+
+http:
+	$(CXX) $(SOURCE_HTTP) $(LDFLAGS_COMMON) $(LDFLAGS_HTTP) $(LPATH_COMMON) $(LPATH_HTTP) $(LLIB_COMMON) $(LLIB_HTTP) -o $(EXEC_HTTP)
+https:
+	$(CXX) $(SOURCE_HTTPS) $(LDFLAGS_COMMON) $(LDFLAGS_HTTPS) $(LPATH_COMMON) $(LPATH_HTTPS) $(LLIB_COMMON) $(LLIB_HTTPS) -o $(EXEC_HTTPS)
+
+clean:
+	rm -f $(EXEC_HTTP) $(EXEC_HTTPS) *.o