build: support clang-cl compiler

Author: dmehala

CMakeLists.txt

@@ -53,7 +53,7 @@ unset(DD_TRACE_VERSION_CPP_CONTENTS)
 
 message(STATUS "dd-trace-cpp transport=${DD_TRACE_TRANSPORT}")
 
-if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC" OR (CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND CMAKE_CXX_COMPILER_FRONTEND_VARIANT MATCHES "MSVC"))
   if (BUILD_SHARED_LIBS AND BUILD_STATIC_LIBS)
     message(FATAL_ERROR "Can't build both static and shared libary for MSVC")
   endif ()