rust: add a patch backported from LLVM 17.0.3 for powerpc.

This gets us back to building rust with the internal LLVM
on NetBSD/macppc.  Ref.
rust-lang/rust#116845

Author: he32

rust/distinfo

@@ -130,6 +130,7 @@ SHA1 (patch-src_llvm-project_llvm_cmake_modules_AddLLVM.cmake) = e1b2eb2f0b3cf1c
 SHA1 (patch-src_llvm-project_llvm_include_llvm-c_DataTypes.h) = cb011fc19957883c01725797f7c85ed1b20f96f1
 SHA1 (patch-src_llvm-project_llvm_include_llvm_Analysis_ConstantFolding.h) = 39d76e6659143d154ae690ac70781b698a2023d8
 SHA1 (patch-src_llvm-project_llvm_lib_Support_BLAKE3_blake3__impl.h) = 67e93f198258a5b59580be20ff47ce58b146c5d5
+SHA1 (patch-src_llvm-project_llvm_lib_Target_PowerPC_PPCISelLowering.cpp) = b68197c1486a4dc40154b3b23dfd55d44048a2d2
 SHA1 (patch-src_llvm-project_llvm_utils_FileCheck_FileCheck.cpp) = 2587c2f4d11ad8f75bf8a16de625135b26bacc15
 SHA1 (patch-src_tools_cargo_src_cargo_core_profiles.rs) = e1af7fde97416e0a269ee34efd37f4f47fcf7a95
 SHA1 (patch-src_tools_cargo_tests_testsuite_build.rs) = 60713699c968f3e389f486e796009d31a5048906

rust/patches/patch-src_llvm-project_llvm_lib_Target_PowerPC_PPCISelLowering.cpp

@@ -0,0 +1,17 @@
+$NetBSD$
+
+Backport change from LLVM 17.0.3, so that rust builds
+with the embedded LLVM.
+Ref. https://github.com/rust-lang/rust/issues/116845.
+
+--- src/llvm-project/llvm/lib/Target/PowerPC/PPCISelLowering.cpp.orig	2023-10-03 02:52:40.000000000 +0000
++++ src/llvm-project/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+@@ -15527,7 +15527,7 @@ SDValue PPCTargetLowering::PerformDAGCom
+       break;
+     SDValue ConstOp = DAG.getConstant(Imm, dl, MVT::i32);
+     SDValue NarrowAnd = DAG.getNode(ISD::AND, dl, MVT::i32, NarrowOp, ConstOp);
+-    return DAG.getAnyExtOrTrunc(NarrowAnd, dl, N->getValueType(0));
++    return DAG.getZExtOrTrunc(NarrowAnd, dl, N->getValueType(0));
+   }
+   case ISD::SHL:
+     return combineSHL(N, DCI);