Fix for old CMake

cmake/Modules/FindGNURADIO.cmake

@@ -416,7 +416,11 @@ if(GNURADIO_RUNTIME_INCLUDE_DIRS)
                 PURPOSE "Required by GNU Radio."
                 TYPE REQUIRED
             )
-            target_link_libraries(Gnuradio::filter INTERFACE Log4cpp::log4cpp)
+            if(CMAKE_VERSION VERSION_GREATER 3.0)
+                target_link_libraries(Gnuradio::filter INTERFACE Log4cpp::log4cpp)
+            else()
+                set(LOG4CPP_WITH_OLD_CMAKE TRUE)
+            endif()
         endif()
         if(${_uses_spdlog})
             find_package(spdlog REQUIRED CONFIG)

src/algorithms/input_filter/gnuradio_blocks/CMakeLists.txt

@@ -53,6 +53,13 @@ target_include_directories(input_filter_gr_blocks
         ${GNSSSDR_SOURCE_DIR}/src/core/interfaces
 )
 
+if(LOG4CPP_WITH_OLD_CMAKE)
+    target_link_libraries(input_filter_gr_blocks
+        PRIVATE
+        Log4cpp::log4cpp
+    )
+endif()
+
 if(GNURADIO_USES_STD_POINTERS)
     target_compile_definitions(input_filter_gr_blocks
         PUBLIC -DGNURADIO_USES_STD_POINTERS=1