[llvm] [ARM] Stop gluing ALU nodes to branches / selects (PR #116970)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

I haven't yet managed to pinpoint exactly which function the breakage happens in (I didn't have quite as much time to spend on it today as I had hoped), but the faulty translation unit can be reproduced with https://martin.st/temp/virtual-preproc.c:

```
clang-good -target armv7-linux-gnueabihf -fcf-protection=none -fvisibility=hidden -fno-stack-protector -fno-strict-aliasing -fPIC -fasynchronous-unwind-tables -O2 -mthumb virtual-preproc.c -c -o virtual.o
```
(Not sure if all those `-f` options are needed for triggering the issue, this is the command currently in use at least.)

https://github.com/llvm/llvm-project/pull/116970