[llvm] [Release] Build compiler-rt during Phase 1 on AIX (PR #70672)

[David Tenty via llvm-commits]

================
@@ -417,6 +417,10 @@ function configure_llvmCore() {
     # building itself and any selected runtimes in the second phase.
     if [ "$Phase" -lt "2" ]; then
       runtime_list=""
+      # compiler-rt built-ins needed on AIX to have a functional Phase 1 clang.
----------------
daltenty wrote:

nit: the library name is `builtins`
```suggestion
      # compiler-rt builtins is needed on AIX to have a functional Phase 1 clang.
```

https://github.com/llvm/llvm-project/pull/70672