add combined backend sources (#11)

Makefile

@@ -11,8 +11,7 @@ ifeq ($(OS), Windows_NT)
 	cd rawpty; $(MAKE) -f Makefile
 	cd hvpty; $(MAKE) -f Makefile.frontend
 else
-	cd wslbridge; $(MAKE) -f Makefile.backend
-	cd hvpty; $(MAKE) -f Makefile.backend
+	cd src; $(MAKE) -f Makefile.backend
 endif
 
 clean:

src/Makefile.backend

@@ -0,0 +1,33 @@
+# This file is part of wslbridge2 project.
+# Licensed under the terms of the GNU General Public License v3 or later.
+# Copyright (C) 2019 Biswapriyo Nath.
+
+# Makefile for wslbridge2 backend
+
+STRIP ?= strip
+NAME = wslbridge2-backend
+BINDIR = ../bin
+CFLAGS = -D_GNU_SOURCE -fno-exceptions -O2 -std=c++11 -Wall
+LFLAGS = -lutil
+
+ifdef RELEASE
+LFLAGS += -static -static-libgcc -static-libstdc++
+endif
+
+BINS = \
+$(BINDIR)/wslbridge2-backend.o
+
+all : $(BINDIR) $(NAME)
+
+$(NAME) : $(BINS)
+	$(CXX) $^ $(LFLAGS) -o $(BINDIR)/$@
+	$(STRIP) $(BINDIR)/$@
+
+$(BINDIR)/wslbridge2-backend.o : wslbridge2-backend.cpp
+	$(CXX) -c $(CFLAGS) $< -o $@
+
+$(BINDIR) :
+	mkdir -p $(BINDIR)
+
+clean :
+	rm -f $(BINDIR)/$(NAME)