LLVM 20.1 bazel has unresolved cyclic dependency in `CodeGen`

[corpoverlords]

Hello,

The Bazel build for LLVM 20.1 seems to have incorrect dep tree compared to the CMake build for CodeGen.

Sometimes I see the error:

bazel-out/k8-fastbuild/bin/external/llvm-project/llvm/libCodeGen.a(ARMException.pic.o)(.data+0x158): error: undefined reference to 'typeinfo for llvm::ARMTargetStreamer'

With single-pass linkers like gold.

This is due to ARMTargetStreamer not in the CodeGen target but in ARMCodeGen target. However, ARMCodeGen depends on CodeGen and there is a cyclic dependency which must be broken.

I don't know what is the best fix...