Rollup merge of #127905 - BKPepe:powerpc-muslspe, r=wesleywiser

Add powerpc-unknown-linux-muslspe compile target

This is almost identical to already existing targets:
- powerpc_unknown_linux_musl.rs
- powerpc_unknown_linux_gnuspe.rs

It has support for PowerPC SPE (muslspe), which
can be used with GCC version up to 8. It is useful for Freescale or IBM cores like e500.

This was verified to be working with OpenWrt build system for CZ.NIC's Turris 1.x routers, which are using Freescale P2020, e500v2, so add it as a Tier 3 target.

Follow-up of https://github.com/rust-lang/rust/pull/100860

compiler/rustc_target/src/spec/mod.rs

@@ -1561,6 +1561,7 @@ supported_targets! {
     ("powerpc-unknown-linux-gnu", powerpc_unknown_linux_gnu),
     ("powerpc-unknown-linux-gnuspe", powerpc_unknown_linux_gnuspe),
     ("powerpc-unknown-linux-musl", powerpc_unknown_linux_musl),
+    ("powerpc-unknown-linux-muslspe", powerpc_unknown_linux_muslspe),
     ("powerpc64-ibm-aix", powerpc64_ibm_aix),
     ("powerpc64-unknown-linux-gnu", powerpc64_unknown_linux_gnu),
     ("powerpc64-unknown-linux-musl", powerpc64_unknown_linux_musl),

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

@@ -0,0 +1,28 @@
+use crate::abi::Endian;
+use crate::spec::{base, Cc, LinkerFlavor, Lld, StackProbeType, Target, TargetOptions};
+
+pub fn target() -> Target {
+    let mut base = base::linux_musl::opts();
+    base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-mspe"]);
+    base.max_atomic_width = Some(32);
+    base.stack_probes = StackProbeType::Inline;
+
+    Target {
+        llvm_target: "powerpc-unknown-linux-muslspe".into(),
+        metadata: crate::spec::TargetMetadata {
+            description: Some("PowerPC SPE Linux with musl".into()),
+            tier: Some(3),
+            host_tools: Some(false),
+            std: Some(true),
+        },
+        pointer_width: 32,
+        data_layout: "E-m:e-p:32:32-Fn32-i64:64-n32".into(),
+        arch: "powerpc".into(),
+        options: TargetOptions {
+            abi: "spe".into(),
+            endian: Endian::Big,
+            mcount: "_mcount".into(),
+            ..base
+        },
+    }
+}