[AIX] Try to not use LLVM tools while building runtimes

Since 64-bit XCOFF and the big AR format is not yet supported in some of these tools, this patch avoids additional setup of these tools. This patch is not intended to prevent picking up the LLVM tools if they happen to be available otherwise.

Reviewed By: hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D85329

Author: daltenty

llvm/runtimes/CMakeLists.txt

@@ -298,6 +298,11 @@ ${error} Set RUNTIMES_BUILD_ALLOW_DARWIN to allow a single darwin triple.")
       endif()
     endforeach()
 
+    # 64-bit XCOFF and big AR format is not yet supported in some of these tools.
+    if(NOT target MATCHES aix)
+      set(${target}_toolchain_tools lld llvm-ar llvm-lipo llvm-ranlib llvm-nm llvm-objcopy llvm-objdump llvm-strip)
+    endif()
+
     llvm_ExternalProject_Add(builtins-${target}
                              ${compiler_rt_path}/lib/builtins
                              DEPENDS ${ARG_DEPENDS}
@@ -311,6 +316,7 @@ ${error} Set RUNTIMES_BUILD_ALLOW_DARWIN to allow a single darwin triple.")
                                         -DCMAKE_ASM_COMPILER_WORKS=ON
                                         -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
                                         ${${target}_extra_args}
+                             TOOLCHAIN_TOOLS clang ${${target}_toolchain_tools}
                              USE_TOOLCHAIN
                              ${EXTRA_ARGS})
   endfunction()
@@ -518,6 +524,11 @@ ${error} Set RUNTIMES_BUILD_ALLOW_DARWIN to allow a single darwin triple.")
       list(APPEND EXTRA_ARGS STRIP_TOOL ${CMAKE_CURRENT_BINARY_DIR}/llvm-strip-link)
     endif()
 
+    # 64-bit XCOFF and big AR format is not yet supported in some of these tools.
+    if(NOT target MATCHES aix)
+      set(${name}_toolchain_tools lld llvm-ar llvm-lipo llvm-ranlib llvm-nm llvm-objcopy llvm-objdump llvm-strip)
+    endif()
+
     llvm_ExternalProject_Add(runtimes-${name}
                              ${CMAKE_CURRENT_SOURCE_DIR}
                              DEPENDS ${${name}_deps} ${CXX_HEADER_TARGET}
@@ -536,6 +547,7 @@ ${error} Set RUNTIMES_BUILD_ALLOW_DARWIN to allow a single darwin triple.")
                                         -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
                                         -DLLVM_RUNTIMES_TARGET=${name}
                                         ${${name}_extra_args}
+                             TOOLCHAIN_TOOLS clang ${${name}_toolchain_tools}
                              EXTRA_TARGETS ${${name}_extra_targets}
                                            ${${name}_test_targets}
                              USE_TOOLCHAIN