Fix: [CMake] Don't detect XAudio2 if defines are missing

cmake/FindXaudio2.cmake

@@ -4,6 +4,7 @@ include(CheckCXXSourceCompiles)
 set(CMAKE_REQUIRED_FLAGS "")
 
 check_cxx_source_compiles("
+    #include <cstdio>
     #include <windows.h>
 
     #undef NTDDI_VERSION
@@ -13,6 +14,6 @@ check_cxx_source_compiles("
     #define _WIN32_WINNT     _WIN32_WINNT_WIN8
 
     #include <xaudio2.h>
-    int main() { return 0; }"
+    int main() { printf(\"%s\\\\n\", XAUDIO2_DLL_A); return 0; }"
     XAUDIO2_FOUND
 )