Rollup merge of #145490 - Kobzol:bootstrap-io-tracing, r=jieyouxu

Trace some basic I/O operations in bootstrap

When working on removing the rmeta sysroot copies, it is quite difficult to figure out *why* was did a certain file appear in a given directory. This should help with that a bit.

r? `@jieyouxu`

Author: jieyouxu