[llvm] [TableGen] Allow empty terminator in SequenceToOffsetTable (PR #119751)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

> There is a bunch of warnings I need to deal with: `warning: zero size arrays are an extension [-Wzero-length-array]` that turn into an error when building with MSVC: `error C2466: cannot allocate an array of constant size 0`.
> 
> ```
>     84  extern const uint16_t XCoreSubRegIdxLists[] = {
>     85    /* 0 */ 
>     86  };
> ```

I couldn't think of anything better than to print a dummy default-constructed element if the array would otherwise be empty.

https://github.com/llvm/llvm-project/pull/119751