Do not use zstd compression for Qt6 as there is no built-in decompression

src/klayout.pri

@@ -130,6 +130,11 @@ equals(HAVE_CRONOLOGY, "1") {
   INCLUDEPATH += $$CRONOLOGY_INCLUDE
 }
 
+!lessThan(QT_MAJOR_VERSION, 6) {
+  # internal resource readers to not support zstd so far
+  QMAKE_RESOURCE_FLAGS += --compress-algo zlib
+}
+
 msvc {
 
   QMAKE_CXXFLAGS += \

src/tl/tl/tlStream.cc

@@ -212,9 +212,9 @@ InputStream::InputStream (const std::string &abstract_path)
 
     QByteArray data;
 #if QT_VERSION >= 0x60000
-      if (res.compressionAlgorithm () == QResource::ZlibCompression) {
+    if (res.compressionAlgorithm () == QResource::ZlibCompression) {
 #else
-      if (res.isCompressed ()) {
+    if (res.isCompressed ()) {
 #endif
       data = qUncompress ((const unsigned char *)res.data (), (int)res.size ());
     } else {