Add target_env = "freestanding"

Author: madsmtm

compiler/rustc_target/src/spec/targets/aarch64_nintendo_switch_freestanding.rs

@@ -23,6 +23,7 @@ pub(crate) fn target() -> Target {
             linker: Some("rust-lld".into()),
             link_script: Some(LINKER_SCRIPT.into()),
             os: "horizon".into(),
+            env: "freestanding".into(),
             vendor: "nintendo".into(),
             max_atomic_width: Some(128),
             stack_probes: StackProbeType::Inline,