Auto merge of #42402 - citizen428:create-dump-mir-dir, r=Mark-Simulacrum
Auto merge of #42402 - citizen428:create-dump-mir-dir, r=Mark-Simulacrum

Create directory for dump-mir-dir automatically

Fixes #35543 r? @Mark-Simulacrum

@Mark-Simulacrum I know someone else said that they'll work on this, but it has been 3+ weeks and I had nothing to do and wanted to contribute a bit.

I now added the call to automatically create the directory as discussed, but was wondering how you feel about the suggestion to set a default directory, i.e. `target/mir`?

GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust