list_vmd_make_targets and list_cmake_targets

* This allows one to run 'make posix list_vmd_make_targets' and get output like

>make posix list_vmd_make_targets
[...]
-- Build files have been written to:
/usr/src/debian/px4/Firmware/Firmware.git/build_posix_sitl_default
PX4 CONFIG: /usr/src/debian/px4/Firmware/Firmware.git/build_posix_sitl_default
Scanning dependencies of target list_vmd_make_targets
[100%] List of acceptable 'posix_sitl_default' <viewer_model_debugger> targets:
none
none_iris
none_iris_opt_flow
none_tailsitter
[...]
replay_solo_valgrind
replay_typhoon_h480_valgrind
[100%] Built target list_vmd_make_targets

Or, run 'make list_vmd_make_targets' from the build_posix_* directory.

* This adds the list_cmake_targets make target to print all
cmake targets that one can match with PX4_NO_OPTIMIZATION.
PX4_NO_OPTIMIZATION is ignored (do optimization as normal)
when the CONFIG isn't posix_sitl_*.

* Add comment in Makefile on how/where to find all targets.

CMakeLists.txt

@@ -402,6 +402,19 @@ if (config_io_board)
 	add_subdirectory(src/modules/px4iofirmware)
 endif()
 
+#=============================================================================
+# generate custom target to print for all executable and module cmake targets
+#
+if(all_posix_cmake_targets)
+	list(SORT all_posix_cmake_targets)
+	px4_join(OUT posix_cmake_target_list LIST ${all_posix_cmake_targets} GLUE "\\n")
+	add_custom_target(list_cmake_targets
+		COMMAND sh -c "printf \"${posix_cmake_target_list}\\n\""
+		COMMENT "List of cmake targets that can be matched by PX4_NO_OPTIMIZATION:"
+		VERBATIM
+		)
+endif()
+
 #=============================================================================
 # generate git version
 #