Check C++20 support and update test-stream executable configuration

Author: yhirose

test/CMakeLists.txt

@@ -35,11 +35,14 @@ gtest_discover_tests(httplib-test)
 if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang|AppleClang|MSVC")
     # Check for C++20 support
     include(CheckCXXCompilerFlag)
-    check_cxx_compiler_flag("-std=c++20" COMPILER_SUPPORTS_CXX20)
     if(MSVC)
-        set(COMPILER_SUPPORTS_CXX20 TRUE)
+        check_cxx_compiler_flag("/std:c++20" COMPILER_SUPPORTS_CXX20)
+    else()
+        check_cxx_compiler_flag("-std=c++20" COMPILER_SUPPORTS_CXX20)
     endif()
 
+    message(STATUS "C++20 support: ${COMPILER_SUPPORTS_CXX20}")
+
     if(COMPILER_SUPPORTS_CXX20)
         add_executable(httplib-test-stream test-stream.cc)
         target_compile_features(httplib-test-stream PRIVATE cxx_std_20)
@@ -48,6 +51,7 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang|AppleClang|MSVC")
         )
         target_link_libraries(httplib-test-stream PRIVATE httplib GTest::gtest_main)
         gtest_discover_tests(httplib-test-stream)
+        message(STATUS "Building httplib-test-stream (C++20 streaming tests)")
     else()
         message(STATUS "C++20 not supported, skipping test-stream")
     endif()