cmake: Force searching DirectX headers/libraries outside root path.
cmake: Force searching DirectX headers/libraries outside root path.

Otherwise headers/libraries are never found when cross-compiling.

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