Rollup merge of #74116 - arlosi:aarch64build, r=pietroalbini

Rollup merge of #74116 - arlosi:aarch64build, r=pietroalbini

Fix cross compilation of LLVM to aarch64 Windows targets

When cross-compiling, the LLVM build system recurses to build tools that need to run on the host system. However, since we pass cmake defines to set the compiler and target, LLVM still compiles these tools for the target system, rather than the host. The tools then fail to execute during the LLVM build.

This change sets defines for the tools that need to run on the host (llvm-nm, llvm-tablegen, and llvm-config), so that the LLVM build does not attempt to build them, and instead relies on the tools already built.

If compiling with clang-cl, adds the `--target` option to specify the target triple. MSVC compilers do not require this, since there is a separate compiler binary for each cross-compilation target.

Related issue: #72881
Requires LLVM change: rust-lang/llvm-project#67