Use code model 'medium' for 64-bit RISC-V targets

Author: Disasm

src/librustc_target/spec/riscv64gc_unknown_none_elf.rs

@@ -23,6 +23,7 @@ pub fn target() -> TargetResult {
             executables: true,
             panic_strategy: PanicStrategy::Abort,
             relocation_model: "static".to_string(),
+            code_model: Some("medium".to_string()),
             emit_debug_gdb_scripts: false,
             abi_blacklist: super::riscv_base::abi_blacklist(),
             eliminate_frame_pointer: false,

src/librustc_target/spec/riscv64imac_unknown_none_elf.rs

@@ -23,6 +23,7 @@ pub fn target() -> TargetResult {
             executables: true,
             panic_strategy: PanicStrategy::Abort,
             relocation_model: "static".to_string(),
+            code_model: Some("medium".to_string()),
             emit_debug_gdb_scripts: false,
             abi_blacklist: super::riscv_base::abi_blacklist(),
             eliminate_frame_pointer: false,