[cmake] assign CMAKE_CXX_FLAGS as a string instead of a list

- fix command line -DCMAKE_CXX_FLAGS expansion

spotted by !43

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 742fd05..dda42c7 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -48,7 +48,7 @@ if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" OR CMAKE_COMPILER_IS_GNUCXX)
     include(CheckCXXCompilerFlag)
     check_cxx_compiler_flag(--std=c++${CMAKE_CXX_STANDARD} STD_CXX)
     if (STD_CXX)
-        list(APPEND CMAKE_CXX_FLAGS --std=c++${CMAKE_CXX_STANDARD})
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} --std=c++${CMAKE_CXX_STANDARD}")
     else ()
         message(SEND_ERROR "Requires C++${CMAKE_CXX_STANDARD} or better")
     endif ()