Rollup merge of #127864 - durin42:farewell-3dnow, r=nikic

cleanup: remove support for 3DNow! cpu features

In llvm/llvm-project@f0eb5587ce all support for 3DNow! intrinsics and instructions were removed. Per the commit message there, only AMD chips between 1998 and 2011 or so actually supported these instructions, and they were effectively replaced by SSE which was available on many more chips. I'd be very surprised if anyone had ever used these from Rust.

`@rustbot` label: +llvm-main

compiler/rustc_target/src/spec/targets/x86_64_unknown_none.rs

@@ -18,9 +18,7 @@ pub fn target() -> Target {
         relro_level: RelroLevel::Full,
         linker_flavor: LinkerFlavor::Gnu(Cc::No, Lld::Yes),
         linker: Some("rust-lld".into()),
-        features:
-            "-mmx,-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-3dnow,-3dnowa,-avx,-avx2,+soft-float"
-                .into(),
+        features: "-mmx,-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2,+soft-float".into(),
         supported_sanitizers: SanitizerSet::KCFI | SanitizerSet::KERNELADDRESS,
         disable_redzone: true,
         panic_strategy: PanicStrategy::Abort,