[libc-commits] [libc] [libc][NFC] rename LONG_DOUBLE_IS_DOUBLE into LIBC_LONG_DOUBLE_IS_DOUBLE (PR #73948)

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https://github.com/lntue commented:

Now that I think about it, technically in this case, `long double` and `double` are still 2 different types to the compilers, so `LIBC_LONG_DOUBLE_IS_FLOAT64` should fit better.  WDYT?

https://github.com/llvm/llvm-project/pull/73948