Auto merge of #138148 - onur-ozkan:fix-llvm-bitcode-build, r=jieyouxu

use target compiler on llvm-bitcode-linker

The build compiler is already resolved inside the `ToolBuild` step, so we should pass only the target compilers for `Mode::ToolRustc` tools.

Fixes https://github.com/rust-lang/rust/issues/138123

r? ghost

try-job: dist-powerpc64le-linux