Export symbols init_app_map and list_builtins

See discussion at https://github.com/PX4/Firmware/issues/5756

src/platforms/apps.cpp.in

@@ -10,6 +10,18 @@
 
 #include <cstdlib>
 
+extern "C" {
+
+${builtin_apps_decl_string}
+int shutdown_main(int argc, char *argv[]);
+int list_tasks_main(int argc, char *argv[]);
+int list_files_main(int argc, char *argv[]);
+int list_devices_main(int argc, char *argv[]);
+int list_topics_main(int argc, char *argv[]);
+int sleep_main(int argc, char *argv[]);
+
+}
+
 extern void px4_show_devices(void);
 
 void init_app_map(apps_map_type &apps)

src/platforms/apps.h.in

@@ -5,23 +5,11 @@
 #include "px4_tasks.h"	// px4_main_t
 #include <map>
 
-extern "C" {
-
-${builtin_apps_decl_string}
-int shutdown_main(int argc, char *argv[]);
-int list_tasks_main(int argc, char *argv[]);
-int list_files_main(int argc, char *argv[]);
-int list_devices_main(int argc, char *argv[]);
-int list_topics_main(int argc, char *argv[]);
-int sleep_main(int argc, char *argv[]);
-
-}
-
 // Maps an app name to it's function.
 typedef std::map<std::string, px4_main_t> apps_map_type;
 
 // Initialize an apps map.
-void init_app_map(apps_map_type &apps);
+__EXPORT void init_app_map(apps_map_type &apps);
 
 // List an apps map.
-void list_builtins(apps_map_type &apps);
+__EXPORT void list_builtins(apps_map_type &apps);