Sync codegen defaults with compiler defaults and add a ping message s…

…o they stay in sync

src/bootstrap/defaults/config.codegen.toml

@@ -17,3 +17,5 @@ debug-logging = true
 incremental = true
 # Print backtrace on internal compiler errors during bootstrap
 backtrace-on-ice = true
+# Make the compiler and standard library faster to build, at the expense of a ~20% runtime slowdown.
+lto = "off"

triagebot.toml

@@ -471,6 +471,11 @@ If this was intentional then you can ignore this comment.
 [mentions."src/tools/x"]
 message = "`src/tools/x` was changed. Bump version of Cargo.toml in `src/tools/x` so tidy will suggest installing the new version."
 
+[mentions."src/bootstrap/defaults/config.compiler.toml"]
+message = "This PR changes src/bootstrap/defaults/config.compiler.toml. If appropriate, please also update `config.codegen.toml` so the defaults are in sync."
+[mentions."src/bootstrap/defaults/config.codegen.toml"]
+message = "This PR changes src/bootstrap/defaults/config.codegen.toml. If appropriate, please also update `config.compiler.toml` so the defaults are in sync."
+
 [assign]
 warn_non_default_branch = true
 contributing_url = "https://rustc-dev-guide.rust-lang.org/contributing.html"