Improve linker-flavor detection

Linker drivers such as gcc, clang or lld often have a version postfix, e.g clang-12. The previous logic would not account for this and would fall back to guessing the linker flavor to be the default linker flavor for the target, which causes linker errors when this is not the case. By accounting for the possible version postfix and also considering g++ and clang++, we considerably reduce the amount of times the fallback guess has to be used. To simplify matching check for a version postfix and match against the linker stem without any version postfix. In contrast to gcc, clang supports all architectures in one binary. This means there are no variants like `aarch64-linux-gnu-clang` and there is no need to check for `-clang` variants.
rust-lang · matthiaskrgr · Jan 11, 2023 · Jan 11, 2023 · Jan 11, 2023 · Jan 8, 2023
commit 3bc2970a2e5f80f04ac2c1b1c1e4ec06a001f151
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -1231,12 +1231,21 @@ pub fn linker_and_flavor(sess: &Session) -> (PathBuf, LinkerFlavor) {
                     sess.emit_fatal(errors::LinkerFileStem);
                 });
 
+                // Remove any version postfix.
+                let stem = stem
+                    .rsplit_once('-')
+                    .and_then(|(lhs, rhs)| rhs.chars().all(char::is_numeric).then_some(lhs))
+                    .unwrap_or(stem);
+
+                // GCC can have an optional target prefix.
                 let flavor = if stem == "emcc" {
                     LinkerFlavor::EmCc
                 } else if stem == "gcc"
                     || stem.ends_with("-gcc")
+                    || stem == "g++"
+                    || stem.ends_with("-g++")
                     || stem == "clang"
-                    || stem.ends_with("-clang")
+                    || stem == "clang++"
                 {
                     LinkerFlavor::from_cli(LinkerFlavorCli::Gcc, &sess.target)
                 } else if stem == "wasm-ld" || stem.ends_with("-wasm-ld") {