Auto merge of #75016 - Manishearth:rollup-x553g7j, r=Manishearth

Rollup of 6 pull requests

Successful merges:

 - #74977 (Clean up E0741 error explanation)
 - #74981 (Some fixes for `plugin.md` in unstable-book)
 - #74983 (Replace a recursive algorithm with an iterative one and a stack.)
 - #74995 (Update the WASI libc build to LLVM 10.)
 - #74996 (submodules: update cargo from 974eb438d to 2d5c2381e)
 - #75007 (Clean up E0743 explanation)

Failed merges:

r? @ghost