core: Add libc++ compatibility (#73)

src/renderer/AsyncResourceGatherer.cpp:98:22: error: no viable overloaded '+='
   98 |             progress += 1.0 / (preloads + 1.0);
      |             ~~~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~~~~
src/renderer/widgets/IWidget.cpp:41:44: error: no member named 'current_zone' in namespace 'std::chrono'
   41 |     const auto current_zone = std::chrono::current_zone();
      |                               ~~~~~~~~~~~~~^

src/renderer/AsyncResourceGatherer.cpp

@@ -95,7 +95,11 @@ void CAsyncResourceGatherer::gather() {
     progress = 0;
     for (auto& c : CWIDGETS) {
         if (c.type == "background") {
+#if defined(_LIBCPP_VERSION) && _LIBCPP_VERSION < 180100
+            progress = progress + 1.0 / (preloads + 1.0);
+#else
             progress += 1.0 / (preloads + 1.0);
+#endif
 
             std::string path = std::any_cast<Hyprlang::STRING>(c.values.at("path"));
 

src/renderer/widgets/IWidget.cpp

@@ -4,6 +4,16 @@
 #include <chrono>
 #include <unistd.h>
 
+#if defined(_LIBCPP_VERSION) && _LIBCPP_VERSION < 190100
+#pragma comment(lib, "date-tz")
+#include <date/tz.h>
+namespace std {
+    namespace chrono {
+        using date::current_zone;
+    }
+}
+#endif
+
 Vector2D IWidget::posFromHVAlign(const Vector2D& viewport, const Vector2D& size, const Vector2D& offset, const std::string& halign, const std::string& valign) {
     Vector2D pos = offset;
     if (halign == "center")