BUG: fix CLICounter terminal output

On my terminal emulator the previous solution always duplicate the
last character of the last line printed by CLICounter. This simplifies
the implementation and fixes the issue.

Instead than overwriting the previous line with white space, this
implementation uses the ANSI escape character to ask the terminal
emulator to clear the line. The emulation for this on the Windows
console is supported by colorama, which we already initialize.

Author: dnicolodi

mesonpy/_util.py

@@ -8,6 +8,7 @@
 
 import contextlib
 import gzip
+import itertools
 import os
 import sys
 import tarfile
@@ -73,22 +74,18 @@ def create_targz(path: Path) -> Iterator[Tuple[tarfile.TarFile, Optional[int]]]:
 class CLICounter:
     def __init__(self, total: int) -> None:
         self._total = total - 1
-        self._count = -1
-        self._current_line = ''
+        self._count = itertools.count()
 
     def update(self, description: str) -> None:
-        self._count += 1
-        new_line = f'[{self._count}/{self._total}] {description}'
+        line = f'[{next(self._count)}/{self._total}] {description}'
         if sys.stdout.isatty():
-            pad_size = abs(len(self._current_line) - len(new_line))
-            print(' ' + new_line + ' ' * pad_size, end='\r', flush=True)
+            print('\r', line, sep='', end='\33[0K', flush=True)
         else:
-            print(new_line)
-        self._current_line = new_line
+            print(line)
 
     def finish(self) -> None:
         if sys.stdout.isatty():
-            print(f'\r{self._current_line}')
+            print()
 
 
 @contextlib.contextmanager