[libc++][libc++abi] Minor follow-up changes after ptrauth upstreaming (#87481)

This patch applies the comments provided on #84573. This is done as a
separate PR to avoid merge conflicts with downstreams that already had
ptrauth support.

NOKEYCHECK=True
GitOrigin-RevId: e64e745e8fb802ffb06259b1a5ba3db713a17087
1 file changed