[compiler-rt] [NFC][sanitizer] Reopen '/proc/%d/task' instead of seek (PR #111899)

[Nico Weber via llvm-commits]

nico wrote:

> > LGTM, what is the motivation for this?
> 
> Browsing code looking for cause of false leak reports.

This broke some of our tests: https://crbug.com/375489584 Could you take a look?

https://github.com/llvm/llvm-project/pull/111899