disable build test on default when using cmake

.github/workflows/ci.yml

@@ -147,6 +147,6 @@ jobs:
     steps:
     - uses: actions/checkout@v4
     - uses: hendrikmuhs/[email protected]
-    - run: cmake -Bbuild -DBUILD_DEPS=ON -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
+    - run: cmake -Bbuild -DBUILD_DEPS=ON -DBUILD_TESTING=ON -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
     - run: cmake --build build --parallel $(nproc)
     - run: ctest --test-dir build --output-on-failure --parallel $(nproc)

CMakeLists.txt

@@ -7,9 +7,8 @@ include(CMakePackageConfigHelpers)  # for write_basic_package_version_file
 
 option(BUILD_DEPS "Use FetchContent download and build dependencies" OFF)
 
-if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+if(BUILD_TESTING AND CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   set(CMAKE_CXX_STANDARD 20)
-  set(BUILD_TESTING ON)
 endif()
 
 if(BUILD_DEPS)