Auto merge of #116486 - van-ema:master, r=nikic

Fix to register analysis passes with -Zllvm-plugins at link-time

This PR fixes an unexpected behavior of the `-Zllvm-plugins` flag. It allows to run an out-of-tree pass as part of LTO.
However, analysis passes are registered before the plugin is loaded. As a result an analysis pass, which is passed as a plugin, is not registered. This causes the LLVM PassManager to fail when the analysis pass is queried from a transformation pass  [(here)](https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/IR/PassManager.h#L776).

This fix mimics the bahavior in [LLVM LTOBackend.cpp](https://github.com/llvm/llvm-project/blob/main/llvm/lib/LTO/LTOBackend.cpp#L273) by loading the plugin before the analysis passes are registered.

Tested with rustc 1.60 and 1.65 and LLVM-13.0.1.

Author: bors