Rollup merge of rust-lang#136700 - RalfJung:hurd, r=Noratrieb

i686-unknown-hurd-gnu: bump baseline CPU to Pentium 4

See rust-lang#136495 for context. ``@sthibaul`` (the only listed target maintainer) said they would be [fine](rust-lang#136495 (comment)) with this change.

compiler/rustc_target/src/spec/targets/i686_unknown_hurd_gnu.rs

@@ -2,7 +2,7 @@ use crate::spec::{Cc, LinkerFlavor, Lld, StackProbeType, Target, base};
 
 pub(crate) fn target() -> Target {
     let mut base = base::hurd_gnu::opts();
-    base.cpu = "pentiumpro".into();
+    base.cpu = "pentium4".into();
     base.max_atomic_width = Some(64);
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-m32"]);
     base.stack_probes = StackProbeType::Inline;

src/doc/rustc/src/platform-support.md

@@ -312,7 +312,7 @@ target | std | host | notes
 [`i586-unknown-netbsd`](platform-support/netbsd.md) | ✓ |  | 32-bit x86 (original Pentium) [^x86_32-floats-x87]
 [`i686-apple-darwin`](platform-support/apple-darwin.md) | ✓ | ✓ | 32-bit macOS (10.12+, Sierra+, Penryn) [^x86_32-floats-return-ABI]
 `i686-unknown-haiku` | ✓ | ✓ | 32-bit Haiku (Pentium 4) [^x86_32-floats-return-ABI]
-[`i686-unknown-hurd-gnu`](platform-support/hurd.md) | ✓ | ✓ | 32-bit GNU/Hurd (PentiumPro) [^x86_32-floats-x87]
+[`i686-unknown-hurd-gnu`](platform-support/hurd.md) | ✓ | ✓ | 32-bit GNU/Hurd (Pentium 4) [^x86_32-floats-x87]
 [`i686-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | NetBSD/i386 (Pentium 4) [^x86_32-floats-return-ABI]
 [`i686-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | 32-bit OpenBSD (Pentium 4) [^x86_32-floats-return-ABI]
 [`i686-unknown-redox`](platform-support/redox.md) | ✓ |  | i686 Redox OS (PentiumPro) [^x86_32-floats-x87]