[llvm] [Offload] define MSVC byte-order macros for rtl endianness checks (PR #202540)

[Joseph Huber via llvm-commits]

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@@ -33,6 +33,13 @@
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/raw_ostream.h"
 
+// TODO: Replace with a shared runtime endianness abstraction.
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jhuber6 wrote:

I'd prefer to handle this as an `|| _WIN32`. You can either remove the macro presence check or just let it pass with _WIN32.

https://github.com/llvm/llvm-project/pull/202540