Change the default value for SPDLOG_BUILD_xxx

The value based on whether spdlog is used as a third-party dependency or
as a standalone project. If spdlog is included through add_subdirectory,
the tests/examples/benchmarsk are disabled by default, and if spdlog is
configured standalone, then they are enabled by default.

CMakeLists.txt

@@ -45,11 +45,17 @@ include(cmake/sanitizers.cmake)
 add_library(spdlog INTERFACE)
 add_library(spdlog::spdlog ALIAS spdlog)
 
-option(SPDLOG_BUILD_EXAMPLES "Build examples" ON)
-option(SPDLOG_BUILD_BENCH "Build benchmarks" ON)
+# Check if spdlog is being used directly or via add_subdirectory
+set(SPDLOG_MASTER_PROJECT OFF)
+if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
+  set(SPDLOG_MASTER_PROJECT ON)
+endif()
+
+option(SPDLOG_BUILD_EXAMPLES "Build examples" ${SPDLOG_MASTER_PROJECT})
+option(SPDLOG_BUILD_BENCH "Build benchmarks" ${SPDLOG_MASTER_PROJECT})
 
 cmake_dependent_option(SPDLOG_BUILD_TESTING
-    "Build spdlog tests" ON
+    "Build spdlog tests" ${SPDLOG_MASTER_PROJECT}
     "BUILD_TESTING" OFF
 )