Allow to build LLVM and wamrc on MinGW (#1013)

Use sysconfig.get_platform() to check whether the platform is MinGW,
and link necessary libraries to wamrc on MinGW.

wamr-compiler/CMakeLists.txt

@@ -250,6 +250,9 @@ add_executable (wamrc main.c)
 if (NOT MSVC)
   target_link_libraries (wamrc aotclib vmlib LLVMDemangle ${LLVM_AVAILABLE_LIBS} ${lib_ubsan}
                          -lm -ldl -lpthread ${lib_lldb})
+  if (MINGW)
+      target_link_libraries (wamrc -lssp -lWs2_32)
+  endif()
 else()
   target_link_libraries (wamrc aotclib vmlib  ${lib_lldb} ${LLVM_AVAILABLE_LIBS} ${lib_ubsan})
 endif()