src/poky:rust: Fix build break because of "download-rustc" and "llvm-tools"

>From Rust 1.84, the download-rustc and llvm-tools options were set to True
(previously they were False)

rust-lang/rust@cce6f03
(download-rustc)

rust-lang/rust@38f0c09
(llvm-tools)

For tarball sources, the download-rustc option should be False, so it has been
reverted back to False.

Setting llvm-tools to True caused issues with finding llvm-objcopy, so this
has been changed back to False.

Upstream-Status: rust-lang/rust#134240

(From OE-Core rev: 2eb952d839e72c24a4180a57631c77910a0da980)

Signed-off-by: Deepesh Varatharajan <Deepesh.Varatharajanwindriver.com>
Signed-off-by: Richard Purdie <richard.purdielinuxfoundation.org>

Author: Deepesh Varatharajan