[clang] [clang][PowerPC] Add flag to enable compatibility with GNU for complex arguments (PR #77732)

[Amy Kwan via cfe-commits]

================
@@ -271,22 +271,33 @@ namespace {
 class PPC32_SVR4_ABIInfo : public DefaultABIInfo {
   bool IsSoftFloatABI;
   bool IsRetSmallStructInRegABI;
+  bool isComplexInRegABI;
+  // Size of GPR in bits
----------------
amy-kwan wrote:

```suggestion
  bool IsComplexInRegABI;
  // Size of GPR in bits.
```
End sentence with a period, and capitalize the boolean variable for consistency.

https://github.com/llvm/llvm-project/pull/77732