[cfi][CodeGen] Call SetLLVMFunctionAttributes{,ForDefinition} on __cf… (#78253)

…i_check

This causes __cfi_check, just as __cfi_check_fail, to get the proper
target-specific attributes, in particular uwtable for unwind table
generation. Previously, nounwind attribute could be inferred for
__cfi_check, which caused it to lose its unwind table even with
-funwind-table option.

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Huawei RRI, OS Lab

Co-authored-by: Nikolai Kholiavin <kholiavin.nikolai@huawei-partners.com>