rust: procedural macros do not support LTO

Attempting to use LTO on a procedural macro crate fails with

  error: lto cannot be used for proc-macro crate type without -Zdylib-lto

Automatically override -Db_lto in the rust.proc_macro method.

Signed-off-by: Paolo Bonzini <[email protected]>

Author: bonzini

mesonbuild/modules/rust.py

@@ -497,6 +497,8 @@ def proc_macro(self, state: ModuleState, args: T.Tuple[str, SourcesVarargsType],
         kwargs['native'] = MachineChoice.BUILD
         kwargs['rust_crate_type'] = 'proc-macro'
         kwargs['rust_args'] = kwargs['rust_args'] + ['--extern', 'proc_macro']
+        kwargs.setdefault('override_options', {})
+        kwargs['override_options']['b_lto'] = False
         target = state._interpreter.build_target(state.current_node, args, kwargs, SharedLibrary)
         return target