add support for mingw64 build

Makefile

@@ -1,7 +1,7 @@
-CC=gcc
-CXX=g++
-CFLAGS=-O3
-CXXFLAGS=-O3
+CC ?= gcc
+CXX ?= g++
+CFLAGS=$(MINGWPATHS) -O3
+CXXFLAGS=-std=c++17 $(MINGWPATHS) -O3
 DEPS = src/compress.h src/stringutils.h
 LIBS=-llzma
 OBJECTS = build/compress.o build/stringutils.o
@@ -17,11 +17,11 @@ build/%.o: src/%.c $(DEPS)
 
 build/%.o: src/%.cpp $(DEPS)
 	$(MAKE_BUILD_FOLDER)
-	$(CXX) -c -o $@ $< $(CFLAGS)
+	$(CXX) -c -o $@ $< $(CXXFLAGS)
 
 build/compress_measurements: $(OBJECTS) src/compress_measurements.cpp
 	$(MAKE_BUILD_FOLDER)
-	$(CXX) -o $@ $^ $(LIBS) $(CFLAGS)
+	$(CXX) -static -o $@ $^ $(LIBS) $(CXXFLAGS)
 
 clean:
 	-rm -rf build