add mipsel_unknown_none target

compiler/rustc_target/src/spec/mipsel_unknown_none.rs

@@ -0,0 +1,32 @@
+// Bare MIPS32r2, little endian, softfloat
+// can be used for MIPS M4K core (e.g. on PIC32MX devices)
+
+use crate::spec::{LinkerFlavor, LldFlavor, RelocModel};
+use crate::spec::{PanicStrategy, Target, TargetOptions};
+
+pub fn target() -> Target {
+    Target {
+        llvm_target: "mipsel-unknown-none".to_string(),
+        target_endian: "little".to_string(),
+        pointer_width: 32,
+        target_c_int_width: "32".to_string(),
+        data_layout: "e-m:m-p:32:32-i8:8:32-i16:16:32-i64:64-n32-S64".to_string(),
+        arch: "mips".to_string(),
+        target_os: "none".to_string(),
+        target_env: String::new(),
+        target_vendor: String::new(),
+        linker_flavor: LinkerFlavor::Lld(LldFlavor::Ld),
+
+        options: TargetOptions {
+            cpu: "mips32r2".to_string(),
+            features: "+mips32r2,+soft-float,+noabicalls".to_string(),
+            max_atomic_width: Some(32),
+            executables: true,
+            linker: Some("rust-lld".to_owned()),
+            panic_strategy: PanicStrategy::Abort,
+            relocation_model: RelocModel::Static,
+            emit_debug_gdb_scripts: false,
+            ..Default::default()
+        },
+    }
+}

compiler/rustc_target/src/spec/mod.rs

@@ -653,6 +653,7 @@ fn $module() {
     ("powerpc64-wrs-vxworks", powerpc64_wrs_vxworks),
 
     ("mipsel-sony-psp", mipsel_sony_psp),
+    ("mipsel-unknown-none", mipsel_unknown_none),
     ("thumbv4t-none-eabi", thumbv4t_none_eabi),
 }