Move TARGET const out of crate root

build.rs

@@ -6,11 +6,10 @@ use std::path::Path;
 fn main() -> io::Result<()> {
     let out_dir = env::var_os("OUT_DIR").unwrap();
     let target = env::var("TARGET").ok();
-    let path = Path::new(&out_dir).join("target.rs");
+    let path = Path::new(&out_dir).join("target");
     let value = match target {
         Some(target) => format!(r#"Some("{}")"#, target.escape_debug()),
         None => "None".to_owned(),
     };
-    let content = format!("const TARGET: Option<&str> = {};", value);
-    fs::write(path, content)
+    fs::write(path, value)
 }

src/cargo.rs

@@ -138,7 +138,7 @@ fn target() -> Vec<&'static str> {
     // Therefore, expose a cfg to always treat the target as host.
     if cfg!(trybuild_no_target) {
         vec![]
-    } else if let Some(target) = crate::TARGET {
+    } else if let Some(target) = include!(concat!(env!("OUT_DIR"), "/target")) {
         vec!["--target", target]
     } else {
         vec![]

src/lib.rs

@@ -245,8 +245,6 @@ mod normalize;
 mod run;
 mod rustflags;
 
-include!(concat!(env!("OUT_DIR"), "/target.rs"));
-
 use std::cell::RefCell;
 use std::panic::RefUnwindSafe;
 use std::path::{Path, PathBuf};