cmake: add hidden option to link components as group

Adds a hidden option to link components in projects as one big group for
debugging purposes. Makes it easy to single out if symbols are not
really defined or some requirements are missing for components leading
to undefined link errors.

tools/cmake/project.cmake

@@ -440,6 +440,10 @@ macro(project project_name)
     add_executable(${project_elf} "${project_elf_src}")
     add_dependencies(${project_elf} _project_elf_src)
 
+    if(__PROJECT_GROUP_LINK_COMPONENTS)
+        target_link_libraries(${project_elf} "-Wl,--start-group")
+    endif()
+
     if(test_components)
         target_link_libraries(${project_elf} "-Wl,--whole-archive")
         foreach(test_component ${test_components})