add scope_guard library as a submodule

A custom CMakeLists.txt is used to create the scope_guard libray. The
original cmake libray file is only used to setup tests.
See ricab/scope_guard#3.

.gitmodules

@@ -3,3 +3,6 @@
 	url = https://github.com/pybind/pybind11
 	branch = smart_holder
 	shallow = true
+[submodule "scope_guard"]
+	path = core/scope_guard/scope_guard
+	url = https://github.com/ricab/scope_guard

core/CMakeLists.txt

@@ -42,6 +42,7 @@ add_compile_options(-fvisibility-inlines-hidden)
 
 set(PROJECT_INCLUDE ${CMAKE_CURRENT_SOURCE_DIR}/include/moveit/task_constructor)
 
+add_subdirectory(scope_guard)
 add_subdirectory(src)
 add_subdirectory(python)
 add_subdirectory(test)

core/scope_guard/CMakeLists.txt

@@ -0,0 +1,16 @@
+cmake_minimum_required(VERSION 3.11) # for FetchContent
+project(scope_guard)
+
+# handle inclusions and dependencies
+include(CheckCXXSymbolExists)
+include(CheckCXXCompilerFlag)
+include(GNUInstallDirs)
+
+
+add_library(scope_guard INTERFACE)
+add_library(scope_guard::scope_guard ALIAS scope_guard) # for consumption via add_subdirectory()
+
+target_include_directories(scope_guard
+  INTERFACE
+    include # assuming we move the header file to an `include` directory
+)

core/scope_guard/include/scope_guard/scope_guard.hpp

@@ -0,0 +1 @@
+../../scope_guard/scope_guard.hpp

core/src/CMakeLists.txt

@@ -37,7 +37,7 @@ add_library(${PROJECT_NAME}
 	solvers/pipeline_planner.cpp
 	solvers/multi_planner.cpp
 )
-target_link_libraries(${PROJECT_NAME} ${catkin_LIBRARIES} fmt::fmt)
+target_link_libraries(${PROJECT_NAME} ${catkin_LIBRARIES} fmt::fmt scope_guard::scope_guard)
 target_include_directories(${PROJECT_NAME}
 	PUBLIC $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
 	PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>