Rollup merge of #57920 - euclio:source-date-epoch, r=Mark-Simulacrum
Rollup merge of #57920 - euclio:source-date-epoch, r=Mark-Simulacrum

use `SOURCE_DATE_EPOCH` for man page time if set

Fixes #57776.

graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust