Fix llvm-for-windows-on-linux build after LLVM r272701.

[thakis]

Summary

The file is called "intrin.h". When building targeting Windows on a Linux system, with the SDK mounted in a case-insensitive file system, "Intrin.h" will miss clang's intrin.h header (because that's not in a case-insensitive file system) but then find intrin.h in the Microsoft SDK. clang can't handle the SDK's intrin.h.

(I'm not really trying to build llvm-for-windows on linux, but I'm trying to build chrome-for-windows on linux, and parts of the chrome build depend on parts of the llvm build, so I want to fix this upstream.)

[rnk]

lgtm

[thakis]

309980, thanks!

lib/Support/Atomic.cpp

 using namespace llvm;
 
 #if defined(_MSC_VER)
-#include <Intrin.h>
+#include <intrin.h>
 
-// We must include windows.h after Intrin.h.
+// We must include windows.h after intrin.h.
 #include <windows.h>
 #undef MemoryFence
 #endif