[clang] [FMV][AIX] Implement target_clones (cpu-only) (PR #177428)

[Wael Yehia via cfe-commits]

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+// RUN: %clang_cc1 -triple powerpc-ibm-aix-xcoff -target-cpu pwr7 -emit-llvm %s -o - | FileCheck %s
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w2yehia wrote:

Similar to Sema, I was being consistent with what's currently there: 
```
clang/test/CodeGen/attr-target-clones-riscv.c
clang/test/CodeGen/attr-target-clones-ppc.c
clang/test/CodeGen/attr-target-clones-riscv-invalid.c
clang/test/CodeGen/attr-target-clones.c
clang/test/CodeGen/attr-target-clones-aarch64.c
```
but there are <Target> folders with other FMV (target or target_version) tests.
Please let me know whether you prefer to move my target_clones into the PowerPC folder. Thanks

https://github.com/llvm/llvm-project/pull/177428