Auto merge of #88269 - prconrad:doctest-persist-binaries, r=jyn514

Doctest persist full binaries when persisting

Tested by adding an extra debug to echo the whole compiler line. Trimmed significantly:

Persisted but not running -> full compile so we get binaries (new behavior).
```
$ rustdoc -Zunstable-options --test --persist-doctests doctests --no-run --extern t=libt.rlib t.rs

DEBUG rustdoc::doctest run_test compiler "rustc" "--crate-type" "bin" "--edition" "2015" "-o" "doctests/t_rs_8_0/rust_out" "--extern" "t=libt.rlib" "-Ccodegen-units=1" "-Z" "unstable-options" "--target" "x86_64-unknown-linux-gnu" "--color" "always"
DEBUG rustdoc::doctest run_test compiler "rustc" "--crate-type" "bin" "--edition" "2015" "-o" "doctests/t_rs_2_0/rust_out" "--extern" "t=libt.rlib" "-Ccodegen-units=1" "-Z" "unstable-options" "--target" "x86_64-unknown-linux-gnu" "--color" "always"
test t.rs - foople (line 2) - compile ... ok
test t.rs - florp (line 8) - compile ... ok
```

Persisted and running -> full compile.
```
$ rustdoc -Zunstable-options --test --persist-doctests doctests --extern t=libt.rlib t.rs

DEBUG rustdoc::doctest run_test compiler "rustc" "--crate-type" "bin" "--edition" "2015" "-o" "doctests/t_rs_8_0/rust_out" "--extern" "t=libt.rlib" "-Ccodegen-units=1" "-Z" "unstable-options" "--target" "x86_64-unknown-linux-gnu" "--color" "always"
DEBUG rustdoc::doctest run_test compiler "rustc" "--crate-type" "bin" "--edition" "2015" "-o" "doctests/t_rs_2_0/rust_out" "--extern" "t=libt.rlib" "-Ccodegen-units=1" "-Z" "unstable-options" "--target" "x86_64-unknown-linux-gnu" "--color" "always"

```

Running but not persisted -> full compile only
```
$ rustdoc --test --extern t=libt.rlib t.rs

DEBUG rustdoc::doctest run_test compiler "rustc" "--crate-type" "bin" "--edition" "2015" "-o" "/tmp/rustdoctestixWAUI/rust_out" "--extern" "t=libt.rlib" "-Ccodegen-units=1" "--target" "x86_64-unknown-linux-gnu" "--color" "always"
DEBUG rustdoc::doctest run_test compiler "rustc" "--crate-type" "bin" "--edition" "2015" "-o" "/tmp/rustdoctestKEaJQu/rust_out" "--extern" "t=libt.rlib" "-Ccodegen-units=1" "--target" "x86_64-unknown-linux-gnu" "--color" "always"

```

Not running and not persisting -> save time and only run metadata.
```
RUSTDOC_LOG=rustdoc=debug,std::test=debug rustdoc -Zunstable-options --no-run --test --extern t=libt.rlib t.rs

DEBUG rustdoc::doctest run_test compiler "rustc" "--crate-type" "bin" "--edition" "2015" "-o" "/tmp/rustdoctest8twt2c/rust_out" "--extern" "t=libt.rlib" "-Ccodegen-units=1" "-Z" "unstable-options" "--emit=metadata" "--target" "x86_64-unknown-linux-gnu" "--color" "always"
DEBUG rustdoc::doctest run_test compiler "rustc" "--crate-type" "bin" "--edition" "2015" "-o" "/tmp/rustdoctest3miSqv/rust_out" "--extern" "t=libt.rlib" "-Ccodegen-units=1" "-Z" "unstable-options" "--emit=metadata" "--target" "x86_64-unknown-linux-gnu" "--color" "always"
```

I can't see any infrastructure for automating this sort of test. Am I missing it?

diff --cc src/librustdoc/doctest.rs
Simple merge