llvm: Disable f128 on powerpc*-aix.

https://github.com/llvm/llvm-project/issues/101545

src/codegen/llvm.zig

@@ -11777,6 +11777,11 @@ fn backendSupportsF128(target: std.Target) bool {
         .mips64el,
         .sparc,
         => false,
+        .powerpc,
+        .powerpcle,
+        .powerpc64,
+        .powerpc64le,
+        => target.os.tag != .aix,
         .aarch64,
         .aarch64_be,
         => std.Target.aarch64.featureSetHas(target.cpu.features, .fp_armv8),