[llvm-exegesis] Fix rGaf658d920e2b

Add missing header.

```
../../llvm/tools/llvm-exegesis/lib/X86/Target.cpp(606,14): error: use of undeclared identifier '__readeflags'
    Eflags = __readeflags();
```

Author: legrosbuffle

llvm/tools/llvm-exegesis/lib/X86/Target.cpp

@@ -28,6 +28,7 @@
 #include <vector>
 #if defined(_MSC_VER)
 #include <immintrin.h>
+#include <intrin.h>
 #endif
 
 namespace llvm {