Add rustc-link-arg-bin key to specify per-bin link args.

Author: Dirbaio

src/cargo/core/compiler/custom_build.rs

@@ -571,6 +571,24 @@ impl BuildOutput {
                         warnings.push(format!("cargo:{} requires -Zextra-link-arg flag", key));
                     }
                 }
+                "rustc-link-arg-bin" => {
+                    if extra_link_arg {
+                        let parts = value.splitn(2, "=").collect::<Vec<_>>();
+                        if parts.len() == 2 {
+                            linker_args.push((
+                                LinkType::SingleBin(parts[0].to_string()),
+                                parts[1].to_string(),
+                            ));
+                        } else {
+                            warnings.push(format!(
+                                "cargo:{} has invalid syntax: expected `cargo:{}=BIN=ARG`",
+                                key, key
+                            ));
+                        }
+                    } else {
+                        warnings.push(format!("cargo:{} requires -Zextra-link-arg flag", key));
+                    }
+                }
                 "rustc-link-arg" => {
                     if extra_link_arg {
                         linker_args.push((LinkType::All, value));

src/cargo/core/compiler/mod.rs

@@ -62,11 +62,12 @@ use cargo_util::{paths, ProcessBuilder, ProcessError};
 
 const RUSTDOC_CRATE_VERSION_FLAG: &str = "--crate-version";
 
-#[derive(Copy, Clone, Hash, Debug, PartialEq, Eq)]
+#[derive(Clone, Hash, Debug, PartialEq, Eq)]
 pub enum LinkType {
     All,
     Cdylib,
     Bin,
+    SingleBin(String),
     Test,
     Bench,
     Example,
@@ -78,6 +79,7 @@ impl LinkType {
             LinkType::All => true,
             LinkType::Cdylib => target.is_cdylib(),
             LinkType::Bin => target.is_bin(),
+            LinkType::SingleBin(name) => target.is_bin() && target.name() == name,
             LinkType::Test => target.is_test(),
             LinkType::Bench => target.is_bench(),
             LinkType::Example => target.is_exe_example(),