build: support clang-cl compiler (#169)

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 ()

cmake/compiler/msvc.cmake

@@ -37,10 +37,6 @@ if (DD_TRACE_STATIC_CRT)
   set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
   set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} /MT")
   set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} /MTd")
-  # set_target_properties(dd_trace_cpp-specs
-  #   PROPERTIES
-  #     MSVC_RUNTIME_LIBRARY  "MultiThreaded$<$<CONFIG:Debug>:Debug>"
-  # )
 endif ()
 
 target_compile_options(dd_trace_cpp-specs