[PAC][compiler-rt] Fix init/fini array signing schema (#150691) When `ptrauth_calls` is present but `ptrauth_init_fini` is not, compiler emits raw unsigned pointers in `.init_array`/`.fini_array` sections. Previously, `__do_init`/`__do_fini` pointers, which are explicitly added to the sections, were implicitly signed (due to the presense of `ptrauth_calls`), while all the other pointers in the sections were implicitly added by the compiler and thus non-signed.. As a result, the sections contained a mix of unsigned function pointers and function pointers signed with default signing schema. This patch introduces use of inline assembly for this particular case, so we can manually specify that we do not want to sign the pointers. Note that we cannot use `__builtin_ptrauth_strip` for this purpose since its result is not a constant expression.
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