T GUI tools: guard with cmake option, default off

The T tools offering a GUI use libxft as a dependency. By default, we
try to limit the amount of dependencies, but libxft comes with X11.

Put the GUI tools behind cmake option T_TOOLS_GUI (default: off) to only
build on demand with a cmake option.

common/utils/T/tracer/CMakeLists.txt

@@ -21,30 +21,6 @@ target_link_libraries(extract_output_subframe PRIVATE tracer_utils)
 add_executable(extract extract.c)
 target_link_libraries(extract PRIVATE tracer_utils)
 
-add_executable(textlog textlog.c)
-target_link_libraries(textlog PRIVATE tracer_utils tracer_filter tracer_gui
-                      tracer_logger tracer_view tracer_events)
-
-
-find_library(png png REQUIRED)
-add_executable(enb enb.c)
-target_link_libraries(enb PRIVATE tracer_utils tracer_filter tracer_gui
-                      tracer_logger tracer_view tracer_events)
-target_link_libraries(enb PRIVATE png)
-
-add_executable(ue ue.c)
-target_link_libraries(ue PRIVATE tracer_utils tracer_filter tracer_gui
-                      tracer_logger tracer_view tracer_events)
-target_link_libraries(ue PRIVATE png)
-
-add_executable(vcd vcd.c)
-target_link_libraries(vcd PRIVATE tracer_utils tracer_filter tracer_gui
-                      tracer_logger tracer_view tracer_events)
-
-add_executable(to_vcd to_vcd.c)
-target_link_libraries(to_vcd PRIVATE tracer_utils tracer_filter tracer_gui
-                      tracer_logger tracer_view tracer_events)
-
 add_executable(macpdu2wireshark macpdu2wireshark.c)
 target_link_libraries(macpdu2wireshark PRIVATE tracer_utils)
 
@@ -52,22 +28,52 @@ add_executable(multi multi.c)
 target_link_libraries(multi PRIVATE tracer_utils T)
 target_include_directories(multi PRIVATE ..)
 
-add_executable(gnb gnb.c)
-target_link_libraries(gnb PRIVATE tracer_utils tracer_filter tracer_gui
-                      tracer_logger tracer_view tracer_events)
-target_link_libraries(gnb PRIVATE png)
-
-add_subdirectory(filter)
-add_subdirectory(gui)
-add_subdirectory(logger)
-add_subdirectory(view)
-
 add_custom_target(T_tools)
 add_dependencies(T_tools
-                 record replay extract_config textlog enb ue vcd macpdu2wireshark
-                 extract_input_subframe extract_output_subframe to_vcd extract multi
-                 gnb)
+                 record replay extract_config extract_input_subframe
+                 extract_output_subframe extract macpdu2wireshark multi)
 add_dependencies(nr-softmodem T_tools)
 add_dependencies(nr-uesoftmodem T_tools)
 add_dependencies(lte-softmodem T_tools)
 add_dependencies(lte-uesoftmodem T_tools)
+
+# Some T tracer tools need additional libraries (Xft, also PNG) that come with
+# a long list of dependencies. We put it behind a separate option for
+# GUI-related tools so they can be added on demand, if necessary.
+add_boolean_option(T_TRACER_GUI OFF  "Compile T tracer GUI tools" OFF)
+if(T_TRACER_GUI)
+  add_executable(textlog textlog.c)
+  target_link_libraries(textlog PRIVATE tracer_utils tracer_filter tracer_gui
+                        tracer_logger tracer_view tracer_events)
+
+  find_library(png png REQUIRED)
+  add_executable(enb enb.c)
+  target_link_libraries(enb PRIVATE tracer_utils tracer_filter tracer_gui
+                        tracer_logger tracer_view tracer_events)
+  target_link_libraries(enb PRIVATE png)
+
+  add_executable(gnb gnb.c)
+  target_link_libraries(gnb PRIVATE tracer_utils tracer_filter tracer_gui
+                        tracer_logger tracer_view tracer_events)
+  target_link_libraries(gnb PRIVATE png)
+
+  add_executable(ue ue.c)
+  target_link_libraries(ue PRIVATE tracer_utils tracer_filter tracer_gui
+                        tracer_logger tracer_view tracer_events)
+  target_link_libraries(ue PRIVATE png)
+
+  add_executable(vcd vcd.c)
+  target_link_libraries(vcd PRIVATE tracer_utils tracer_filter tracer_gui
+                        tracer_logger tracer_view tracer_events)
+
+  add_executable(to_vcd to_vcd.c)
+  target_link_libraries(to_vcd PRIVATE tracer_utils tracer_filter tracer_gui
+                        tracer_logger tracer_view tracer_events)
+
+  add_subdirectory(gui)
+  add_subdirectory(filter)
+  add_subdirectory(logger)
+  add_subdirectory(view)
+
+  add_dependencies(T_tools textlog enb gnb ue vcd to_vcd)
+endif()