Only build tests and documentation when building as a top-level project

CMakeLists.txt

@@ -1,17 +1,21 @@
-cmake_minimum_required(VERSION 3.16)
+cmake_minimum_required(VERSION 3.21)
 project(overture VERSION 0.0.1)
 
 option(TEST_DISABLE_FORK "Disable fork() in the testing framework." OFF)
-option(ENABLE_COVERAGE "Enable code coverage build type and target." OFF)
-option(ENABLE_DOXYGEN "Enable code documentation target via Doxygen." ON)
+
+if (PROJECT_IS_TOP_LEVEL)
+    option(ENABLE_COVERAGE "Enable code coverage build type and target." OFF)
+    option(ENABLE_DOXYGEN "Enable code documentation target via Doxygen." ON)
+
+    include(cmake/Coverage.cmake)
+    include(cmake/Doxygen.cmake)
+endif()
 
 add_compile_options(
     $<$<C_COMPILER_ID:GNU,Clang>:-Wall>
     $<$<C_COMPILER_ID:GNU,Clang>:-Wextra>
     $<$<C_COMPILER_ID:GNU,Clang>:-pedantic>)
 
-include(cmake/Coverage.cmake)
-include(cmake/Doxygen.cmake)
 install(
     FILES
         cmake/Coverage.cmake
@@ -26,7 +30,9 @@ set(CMAKE_INTERPROCEDURAL_OPTIMIZATION_RELEASE ON)
 
 add_subdirectory(src)
 
-include(CTest)
-if (BUILD_TESTING)
-    add_subdirectory(test)
+if (PROJECT_IS_TOP_LEVEL)
+    include(CTest)
+    if (BUILD_TESTING)
+        add_subdirectory(test)
+    endif()
 endif()