mlog: Avoid cyclic imports

As utils/platform wants to use mlog, mlog should not sometimes attempt
to depend on mesonlib, as mesonlib will load platform

mesonbuild/mlog.py

@@ -148,7 +148,7 @@ def start_pager(self) -> None:
         except Exception as e:
             # Ignore errors, unless it is a user defined pager.
             if 'PAGER' in os.environ:
-                from .mesonlib import MesonException
+                from .utils.core import MesonException
                 raise MesonException(f'Failed to start pager: {str(e)}')
 
     def stop_pager(self) -> None:
@@ -271,7 +271,7 @@ def _log_error(self, severity: _Severity, *rargs: TV_Loggable,
                    nested: bool = True, sep: T.Optional[str] = None,
                    end: T.Optional[str] = None,
                    is_error: bool = True) -> None:
-        from .mesonlib import MesonException, relpath
+        from .utils.universal import MesonException, relpath
 
         # The typing requirements here are non-obvious. Lists are invariant,
         # therefore T.List[A] and T.List[T.Union[A, B]] are not able to be joined