Sync tools directory

tools/preproc/Makefile

@@ -1,19 +1,25 @@
-CXX := g++
+CXX ?= g++
 
 CXXFLAGS := -std=c++11 -O2 -Wall -Wno-switch -Werror
 
 SRCS := asm_file.cpp c_file.cpp charmap.cpp preproc.cpp string_parser.cpp \
-	utf8.cpp
+	utf8.cpp io.cpp
 
 HEADERS := asm_file.h c_file.h char_util.h charmap.h preproc.h string_parser.h \
-	utf8.h
+	utf8.h io.h
+
+ifeq ($(OS),Windows_NT)
+EXE := .exe
+else
+EXE :=
+endif
 
 .PHONY: all clean
 
-all: preproc
+all: preproc$(EXE)
 	@:
 
-preproc: $(SRCS) $(HEADERS)
+preproc$(EXE): $(SRCS) $(HEADERS)
 	$(CXX) $(CXXFLAGS) $(SRCS) -o $@ $(LDFLAGS)
 
 clean: