bootstrap: make lld default to true

Author: lqd

src/bootstrap/config.rs

@@ -1427,7 +1427,7 @@ impl Config {
                 config.incremental = true;
             }
             set(&mut config.use_lld, rust.use_lld);
-            set(&mut config.lld_enabled, rust.lld);
+            config.lld_enabled = rust.lld.unwrap_or(true);
             set(&mut config.llvm_tools_enabled, rust.llvm_tools);
             config.rustc_parallel = rust.parallel_compiler.unwrap_or(false);
             config.rustc_default_linker = rust.default_linker;