rustc_target: callconv: powerpc64: Use llvm_abiname rather than target_abi for ABI determination

Currently on PowerPC64 targets, llvm_abiname and target_abi will be the
same unless we're on AIX. Since llvm_abiname is what we pass on to LLVM,
it is preferable to use the value of that to determine the calling
convention rather than target_abi.

All PowerPC64 targets set both llvm_abiname and target_abi to the
respective ELF ABIs, with the exception of AIX. This is a non-functional
change.

Author: Gelbpunkt

compiler/rustc_target/src/callconv/powerpc64.rs

@@ -106,9 +106,9 @@ where
     Ty: TyAbiInterface<'a, C> + Copy,
     C: HasDataLayout + HasTargetSpec,
 {
-    let abi = if cx.target_spec().options.abi == Abi::ElfV2 {
+    let abi = if cx.target_spec().options.llvm_abiname == "elfv2" {
         ELFv2
-    } else if cx.target_spec().options.abi == Abi::ElfV1 {
+    } else if cx.target_spec().options.llvm_abiname == "elfv1" {
         ELFv1
     } else if cx.target_spec().os == Os::Aix {
         AIX