Set CFG_RELEASE for tools in bootstrap/tool.rs

Since rustc-ap-* v659 we now need to set CFG_RELEASE for
rustc-ap-rustc_attr for `#[cfg(version(...))]` to work.

Co-authored-by: Eric Huss <[email protected]>

Author: Xanewok

src/bootstrap/tool.rs

@@ -252,6 +252,10 @@ pub fn prepare_tool_cargo(
     // own copy
     cargo.env("LZMA_API_STATIC", "1");
 
+    // CFG_RELEASE is needed by rustfmt (and possibly other tools) which
+    // import rustc-ap-rustc_attr which requires this to be set for the
+    // `#[cfg(version(...))]` attribute.
+    cargo.env("CFG_RELEASE", builder.rust_release());
     cargo.env("CFG_RELEASE_CHANNEL", &builder.config.channel);
     cargo.env("CFG_VERSION", builder.rust_version());
     cargo.env("CFG_RELEASE_NUM", channel::CFG_RELEASE_NUM);