Make the crown disabled warning clearer and less scary (#37535)

Instead of printing a Rust compilation warning, simply print a message
before every build (when using `mach`) that shows the build
configuration and whether or not `crown` is enabled.

Fixes #32597.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

python/servo/build_commands.py

@@ -146,8 +146,9 @@ class MachCommands(CommandBase):
         # Gather Cargo build timings (https://doc.rust-lang.org/cargo/reference/timings.html).
         opts = ["--timings"] + opts
 
+        crown_enabled = "enabled" if kwargs.get("use_crown", False) else "disabled (no JS garbage collection linting)"
+        print(f"Building `{build_type.directory_name()}` build with crown {crown_enabled}.")
         if very_verbose:
-            print(["Calling", "cargo", "build"] + opts)
             for key in env:
                 print((key, env[key]))