Move proc-macro-srv RUSTC_VERSION fetching from include to env var

crates/proc-macro-srv/build.rs

@@ -4,24 +4,12 @@
 use std::{env, fs::File, io::Write, path::PathBuf, process::Command};
 
 fn main() {
-    println!("cargo:rustc-check-cfg=cfg(rust_analyzer)");
-
-    let mut path = PathBuf::from(env::var_os("OUT_DIR").unwrap());
-    path.push("rustc_version.rs");
-    let mut f = File::create(&path).unwrap();
+    println!("cargo::rustc-check-cfg=cfg(rust_analyzer)");
 
     let rustc = env::var("RUSTC").expect("proc-macro-srv's build script expects RUSTC to be set");
     let output = Command::new(rustc).arg("--version").output().expect("rustc --version must run");
     let version_string = std::str::from_utf8(&output.stdout[..])
         .expect("rustc --version output must be UTF-8")
         .trim();
-
-    write!(
-        f,
-        "
-    #[allow(dead_code)]
-    pub(crate) const RUSTC_VERSION_STRING: &str = {version_string:?};
-    "
-    )
-    .unwrap();
+    println!("cargo::rustc-env=RUSTC_VERSION={}", version_string);
 }

crates/proc-macro-srv/src/lib.rs

@@ -48,8 +48,7 @@ use span::Span;
 
 use crate::server::TokenStream;
 
-// see `build.rs`
-include!(concat!(env!("OUT_DIR"), "/rustc_version.rs"));
+pub const RUSTC_VERSION_STRING: &str = env!("RUSTC_VERSION");
 
 trait ProcMacroSrvSpan: Copy {
     type Server: proc_macro::bridge::server::Server<TokenStream = TokenStream<Self>>;