[clang] [llvm] [clang] Add regalloc PBQP for all targets in clang (PR #166645)

[Ivan Shumakov via cfe-commits]

Zararest wrote:

Here are sizes of a clang binary before and after current commit:
```
clang release X86 target: 
100391336 bytes -> 100474456 bytes
+0.082%
```


https://github.com/llvm/llvm-project/pull/166645