add support for mingw64 build

.gitignore

@@ -1 +1,2 @@
 build/
+mingw-w64-x86_64-xz/

Makefile

@@ -1,7 +1,7 @@
 CC=gcc
 CXX=g++
-CFLAGS=-O3
+CFLAGS=$(MINGWPATHS) -O3
-CXXFLAGS=-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

build-linux.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+
+set -e
+
+make clean
+make

build-windows.sh

@@ -0,0 +1,40 @@
+#!/bin/bash
+
+set -e
+
+XZ_DIR="mingw-w64-x86_64-xz"
+XZ_PACKAGE_VERSION_FILE="${XZ_DIR}/version"
+XZ_PACKAGE_VERSION="mingw-w64-x86_64-xz-5.2.5-2-any.pkg.tar.zst"
+
+if [ -f "${XZ_DIR}/version" ]; then
+    XZ_PACKAGE_INSTALLED_VERSION=$(<$XZ_PACKAGE_VERSION_FILE)
+else
+    XZ_PACKAGE_INSTALLED_VERSION=""
+fi
+
+if [ "${XZ_PACKAGE_VERSION}" != "${XZ_PACKAGE_INSTALLED_VERSION}" ]; then
+    rm -rf ${XZ_DIR}
+    mkdir ${XZ_DIR}
+    (cd mingw-w64-x86_64-xz && \
+        wget -qO- https://mirror.msys2.org/mingw/mingw64/${XZ_PACKAGE_VERSION} | \
+        unzstd - | \
+        tar -xf -)
+    echo ${XZ_PACKAGE_VERSION} > ${XZ_PACKAGE_VERSION_FILE}
+fi
+
+export MINGWPATHS="-Imingw-w64-x86_64-xz/mingw64/include -Lmingw-w64-x86_64-xz/mingw64/lib"
+
+case "$(uname -s)" in
+    Linux)
+        export CC="x86_64-w64-mingw32-gcc"
+        export CXX="x86_64-w64-mingw32-g++"
+        ;;
+
+   MINGW*)
+        export CC="gcc"
+        export CXX="g++"
+        ;;
+esac
+
+make clean
+make