Restore BZip2 in nglcompression (legacy REQUIRED it)

Define HAVE_BZIP2 so the real impl compiles instead of the stub; link libbz2; nglcomp_test green

qt6-after/qt6-migrated-legatus/Z/src/nglcompression/CMakeLists.txt

@@ -5,9 +5,8 @@
 # $Author$
 #
 
-# BZip2 stub - libbz2-dev not available, disable bzip2 support
-SET(HAVE_BZIP2 FALSE)
-MESSAGE(STATUS "BZip2 disabled - development headers not available")
+# BZip2 (legacy REQUIRED it; defines HAVE_BZIP2 so the real impl compiles instead of the stub)
+FIND_PACKAGE(BZip2 REQUIRED)
 
 SET(nglcomp_SRCS
   nglcomp_bzip2iodevice.cpp
@@ -25,8 +24,14 @@ NGL_TARGET_LINK_LIBRARIES(nglcompression
   PRIVATE
     Qt6::Concurrent
     NGLLogger
+    ${BZIP2_LIBRARIES}
 )
-# BZip2 disabled - no linking needed
+NGL_TARGET_INCLUDE_DIRECTORIES(nglcompression
+  PRIVATE
+    ${BZIP2_INCLUDE_DIR}
+)
+# Enable the real bzip2 impl (guard in nglcomp_bzip2iodevice.{h,cpp}); legacy always compiled it
+TARGET_COMPILE_DEFINITIONS(nglcompression PRIVATE HAVE_BZIP2)
 NGL_INSTALL_TARGET(nglcompression)
 
 IF(BUILD_WS AND BUILD_TESTING)