Fix --target flag argument order in rustc_cfg fetching

Author: Veykril

crates/project-model/src/toolchain_info/rustc_cfg.rs

@@ -68,10 +68,10 @@ fn rustc_print_cfg(
             cmd.envs(extra_env);
             cmd.env("RUSTC_BOOTSTRAP", "1");
             cmd.args(["rustc", "-Z", "unstable-options"]).args(RUSTC_ARGS);
-            cmd.args(["--", "-O"]);
             if let Some(target) = target {
                 cmd.args(["--target", target]);
             }
+            cmd.args(["--", "-O"]);
 
             match utf8_stdout(&mut cmd) {
                 Ok(it) => return Ok(it),