Add metadata to spec.

Author: royb3

compiler/rustc_target/src/spec/targets/riscv32ima_unknown_none_elf.rs

@@ -4,6 +4,12 @@ pub fn target() -> Target {
     Target {
         data_layout: "e-m:e-p:32:32-i64:64-n32-S128".into(),
         llvm_target: "riscv32".into(),
+        metadata: crate::spec::TargetMetadata {
+            description: None,
+            tier: None,
+            host_tools: None,
+            std: None,
+        },
         pointer_width: 32,
         arch: "riscv32".into(),