[Inliner] Don't count a call penalty for foldable __memcpy_chk and similar (#117876)

When the size is an appropriate constant, __memcpy_chk will turn into a
memcpy that gets folded away by InstComb

[Inliner] Don't count a call penalty for foldable __memcpy_chk and similar (#117876)

When the size is an appropriate constant, __memcpy_chk will turn into a
memcpy that gets folded away by InstCombine. Therefore this patch avoids
counting these as calls for purposes of inlining costs.

This is only really relevant on platforms whose headers redirect memcpy
to __memcpy_chk (such as Darwin). On platforms that use intrinsics,
memcpy and similar functions are already exempt from call penalties.

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