reorder Rust struct's fields based on the order in config.toml.example

Author: Guanqun Lu

src/bootstrap/config.rs

@@ -293,6 +293,7 @@ impl Default for StringOrBool {
 #[serde(deny_unknown_fields, rename_all = "kebab-case")]
 struct Rust {
     optimize: Option<bool>,
+    debug: Option<bool>,
     codegen_units: Option<u32>,
     codegen_units_std: Option<u32>,
     debug_assertions: Option<bool>,
@@ -301,25 +302,24 @@ struct Rust {
     debuginfo_level_std: Option<u32>,
     debuginfo_level_tools: Option<u32>,
     debuginfo_level_tests: Option<u32>,
-    parallel_compiler: Option<bool>,
     backtrace: Option<bool>,
+    incremental: Option<bool>,
+    parallel_compiler: Option<bool>,
     default_linker: Option<String>,
     channel: Option<String>,
     musl_root: Option<String>,
     rpath: Option<bool>,
+    verbose_tests: Option<bool>,
     optimize_tests: Option<bool>,
     codegen_tests: Option<bool>,
     ignore_git: Option<bool>,
-    debug: Option<bool>,
     dist_src: Option<bool>,
-    verbose_tests: Option<bool>,
-    incremental: Option<bool>,
     save_toolstates: Option<String>,
     codegen_backends: Option<Vec<String>>,
     codegen_backends_dir: Option<String>,
     lld: Option<bool>,
-    lldb: Option<bool>,
     llvm_tools: Option<bool>,
+    lldb: Option<bool>,
     deny_warnings: Option<bool>,
     backtrace_on_ice: Option<bool>,
     verify_llvm_ir: Option<bool>,