[llvm] [Object][COFF][NFC] Introduce Arm64ECThunkType enum. (PR #85936)

[Daniel Paoliello via llvm-commits]

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@@ -806,6 +806,12 @@ enum Feat00Flags : uint32_t {
   Kernel = 0x40000000,
 };
 
+enum class Arm64ECThunkType : uint32_t {
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dpaoliello wrote:

Should the underlying type for the enum be `uint8_t`, since that's what we end up casting it to?

https://github.com/llvm/llvm-project/pull/85936