msys2: Fix absolute windows paths

- Ensure path DATA_DIR isn't made absolute during compilation
- Use cygpath to create absolute path at runtime

src/pathHelper.cpp

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: Apache-2.0
+/*
+ * Copyright (C) 2022 Greg Davill <[email protected]>
+ */
+
+#if defined (_WIN64) || defined (_WIN32)
+#include "pathHelper.hpp"
+
+#include <iostream>
+#include <memory>
+#include <string>
+#include <array>
+#include <regex>
+
+std::string PathHelper::absolutePath(std::string input_path) {
+
+    /* Attempt to execute cygpath */
+    std::string cmd = std::string("cygpath -m " + input_path);
+
+    std::array<char, 128> buffer;
+    std::string result;
+    std::unique_ptr<FILE, decltype(&pclose)> pipe(popen(cmd.c_str(), "r"), pclose);
+    if (!pipe) {
+        /* If cygpath fails to run, return original path */
+        return input_path;
+    }
+    while (fgets(buffer.data(), buffer.size(), pipe.get()) != nullptr) {
+        result += buffer.data();
+    }
+
+    /* Trim trailing newline */
+    static const std::regex tws{"[[:space:]]*$", std::regex_constants::extended};
+    return std::regex_replace(result, tws, "");
+}
+
+#endif