Auto merge of #45899 - eddyb:meta-race, r=alexcrichton
Auto merge of #45899 - eddyb:meta-race, r=alexcrichton

rustc_trans: atomically write .rmeta outputs to avoid races.

Fixes #45841 in a similar vein to how LLVM writes archives: write a temporary file and then rename it.

r? @alexcrichton

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