GDAL is a public dependency :(

SimGearConfig.cmake.in

@@ -32,6 +32,10 @@ endif(ENABLE_RTI)
 # Alternative terrain engine based on pagedLOD
 
 set(ENABLE_GDAL @ENABLE_GDAL@)
+if (ENABLE_GDAL)
+  find_dependency(GDAL)
+endif()
+
 set(ENABLE_OPENMP @ENABLE_OPENMP@)
 
 include("${CMAKE_CURRENT_LIST_DIR}/SimGearTargets.cmake")

simgear/CMakeLists.txt

@@ -168,7 +168,9 @@ if(NOT SIMGEAR_HEADLESS)
         ${JPEG_LIBRARY})
 
     if(ENABLE_GDAL)
-        target_link_libraries(SimGearScene PRIVATE GDAL::GDAL)
+        # FIXME: should be RIVATE, but we leak GDAL headers
+        # in our own headers :(
+        target_link_libraries(SimGearScene PUBLIC GDAL::GDAL)
     endif()
 
     # only actually needed by canvas/KeyboardEvent.cxx