Rollup merge of #98708 - pinkforest:rustdoc-fix-98690, r=GuillaumeGomez

Rollup merge of #98708 - pinkforest:rustdoc-fix-98690, r=GuillaumeGomez

rustdoc: fix 98690 Panic if invalid path for -Z persist-doctests

Closes #98690 for rustdoc panic

I changed this to do eprintln and orderly panic instead of unwrap doing unhandled panic

~/gg/rust/build/x86_64-unknown-linux-gnu/stage2/bin/rustdoc --test -Z unstable-options --persist-doctests /tmp/foobar main.rs
Couldn't create directory for doctest executables: Permission denied (os error 13)