Add a sparc-unknown-none-elf target.

Tested with the Gaisler bcc2 toolchain (both gcc and clang) and the Leon3 simulator.

compiler/rustc_target/src/spec/mod.rs

@@ -1433,6 +1433,8 @@ supported_targets! {
     ("riscv64gc-unknown-linux-gnu", riscv64gc_unknown_linux_gnu),
     ("riscv64gc-unknown-linux-musl", riscv64gc_unknown_linux_musl),
 
+    ("sparc-unknown-none-elf", sparc_unknown_none_elf),
+
     ("loongarch64-unknown-none", loongarch64_unknown_none),
     ("loongarch64-unknown-none-softfloat", loongarch64_unknown_none_softfloat),
 

compiler/rustc_target/src/spec/sparc_unknown_none_elf.rs

@@ -0,0 +1,27 @@
+use crate::abi::Endian;
+use crate::spec::{Cc, LinkerFlavor, Lld, PanicStrategy, RelocModel, Target, TargetOptions};
+
+pub fn target() -> Target {
+    let options = TargetOptions {
+        linker_flavor: LinkerFlavor::Gnu(Cc::Yes, Lld::No),
+        linker: Some("sparc-elf-gcc".into()),
+        endian: Endian::Big,
+        cpu: "v7".into(),
+        abi: "elf".into(),
+        max_atomic_width: Some(32),
+        atomic_cas: true,
+        panic_strategy: PanicStrategy::Abort,
+        relocation_model: RelocModel::Static,
+        no_default_libraries: false,
+        emit_debug_gdb_scripts: false,
+        eh_frame_header: false,
+        ..Default::default()
+    };
+    Target {
+        data_layout: "E-m:e-p:32:32-i64:64-f128:64-n32-S64".into(),
+        llvm_target: "sparc-unknown-none-elf".into(),
+        pointer_width: 32,
+        arch: "sparc".into(),
+        options,
+    }
+}