Use -isystem to DirectX SDK headers on MinGW.
Use -isystem to DirectX SDK headers on MinGW.

Otherwise there will be many warnings and duplicate definitions when
using recent DirectX SDK headers.

surround-io/apitrace,tuanthng/apitrace,surround-io/apitrace,PeterLValve/apitrace,trtt/apitrace,tuanthng/apitrace,swq0553/apitrace,joshua5201/apitrace,surround-io/apitrace,EoD/apitrace,tuanthng/apitrace,schulmar/apitrace,swq0553/apitrace,tuanthng/apitrace,apitrace/apitrace,swq0553/apitrace,surround-io/apitrace,EoD/apitrace,schulmar/apitrace,surround-io/apitrace,PeterLValve/apitrace,apitrace/apitrace,EoD/apitrace,apitrace/apitrace,trtt/apitrace,swq0553/apitrace,schulmar/apitrace,EoD/apitrace,PeterLValve/apitrace,PeterLValve/apitrace,EoD/apitrace,trtt/apitrace,joshua5201/apitrace,apitrace/apitrace,joshua5201/apitrace,tuanthng/apitrace,schulmar/apitrace,trtt/apitrace,joshua5201/apitrace,joshua5201/apitrace,swq0553/apitrace,trtt/apitrace,schulmar/apitrace