[runtimes] Remove TOOLCHAIN_TOOLS specialization

{builtin,runtime}_register_target passes a TOOLCHAIN_TOOLS list, whereas
{builtin,runtime}_default_target does notl. The explicit TOOLCHAIN_TOOLS
list matches what LLVMExternalProjectUtils would have set anyway,
barring some target-specific adjustments, and those target-specific
adjustments seem valuable, so let's drop the explicit TOOLCHAIN_TOOLS
list and let LLVMExternalProjectUtils take care of it.

Reviewed By: phosek

Differential Revision: https://reviews.llvm.org/D86366

llvm/runtimes/CMakeLists.txt

@@ -309,7 +309,6 @@ ${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 lld llvm-ar llvm-lipo llvm-ranlib llvm-nm llvm-objcopy llvm-objdump llvm-strip
                              USE_TOOLCHAIN
                              ${EXTRA_ARGS})
   endfunction()
@@ -529,7 +528,6 @@ ${error} Set RUNTIMES_BUILD_ALLOW_DARWIN to allow a single darwin triple.")
                                         -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON
                                         -DLLVM_RUNTIMES_TARGET=${name}
                                         ${${name}_extra_args}
-                             TOOLCHAIN_TOOLS clang lld llvm-ar llvm-lipo llvm-ranlib llvm-nm llvm-objcopy llvm-objdump llvm-strip
                              EXTRA_TARGETS ${${name}_extra_targets}
                                            ${${name}_test_targets}
                              USE_TOOLCHAIN