Rollup merge of #129187 - jieyouxu:squeaky-clean-windows-symlinks, r=Kobzol

bootstrap: fix clean's remove_dir_all implementation

It turns out bootstrap's `clean.rs`'s hand-rolled `rm_rf` (which probably comes before `std::fs::remove_dir_all` was stable) is very broken on native Windows around both read-only files/directories and especially symbolic links. So instead of rolling our own, just use `std::fs::remove_dir_all`.

This is a blocker for compiletest's own `rm_rf` implementation #129155 which happens to be also buggy, which in turn is a blocker for the rmake.rs test port #128562 that heavily exercises symlinks (I was reviewing #128562 and testing it on native Windows which is how I found out).

I also left a FIXME for `detect_src_and_out` due to a failing assertion on native Windows (opened #129188):

```
---- core::config::tests::detect_src_and_out stdout ----
thread 'core::config::tests::detect_src_and_out' panicked at src\core\config\tests.rs:72:13:
assertion `left == right` failed
  left: "E:\\tmp"
 right: "C:\\tmp"
```

Fixes #112544 (because now we handle Windows symlinks properly).

try-job: x86_64-msvc
try-job: i686-mingw
try-job: test-various
try-job: armhf-gnu
try-job: aarch64-apple
try-job: aarch64-gnu

0 files changed, 0 insertions, 0 deletions