Auto merge of #154844 - Walnut356:compiletest_windows, r=jieyouxu

Fix `compiletest` path-related issues on Windows

fixes the issues mentioned [here](https://github.com/rust-lang/rust/pull/147552#issuecomment-4178431869). With these changes I'm able to run `./x test tests/debuginfo` on `x86_64-pc-windows-gnu` without any issues.

As mentioned in the link though, there are 3 tests that currently fail when run on windows, but that pass on whatever CI targets actually run `tests/debuginfo`.

I'm not sure if `target_run_lib_path` really needs to be prepended on all targets (it absolutely does for Windows though), but i figure it can't hurt. Also made sure the path separators are correct per-platform.

The `lldb_batchmode` change prevents the tests from hanging forever. I'm not 100% sure why this hasn't been a problem so far. Maybe just due to the version of LLDB used on the test runner? I haven't done too much testing, but the situation is...weird. I opened [an issue about it in the LLVM repo](https://github.com/llvm/llvm-project/issues/190516).