[utils] `Popen`: Reset PyInstaller environment (#11258)

- Forces spawning independent subprocesses for exes bundled with PyInstaller>=6.10
- Fixes regression introduced in fb8b7f226d
- Ref: https://pyinstaller.org/en/v6.10.0/CHANGES.html#incompatible-changes

Closes #11259
Authored by: bashonly, Grub4K

Co-authored-by: Simon Sawicki <contact@grub4k.xyz>

yt_dlp/utils/_utils.py

@@ -824,14 +824,18 @@ class Popen(subprocess.Popen):
         _startupinfo = None
 
     @staticmethod
-    def _fix_pyinstaller_ld_path(env):
-        """Restore LD_LIBRARY_PATH when using PyInstaller
-            Ref: https://github.com/pyinstaller/pyinstaller/blob/develop/doc/runtime-information.rst#ld_library_path--libpath-considerations
-                 https://github.com/yt-dlp/yt-dlp/issues/4573
-        """
+    def _fix_pyinstaller_issues(env):
         if not hasattr(sys, '_MEIPASS'):
             return
 
+        # Force spawning independent subprocesses for exes bundled with PyInstaller>=6.10
+        # Ref: https://pyinstaller.org/en/v6.10.0/CHANGES.html#incompatible-changes
+        #      https://github.com/yt-dlp/yt-dlp/issues/11259
+        env['PYINSTALLER_RESET_ENVIRONMENT'] = '1'
+
+        # Restore LD_LIBRARY_PATH when using PyInstaller
+        # Ref: https://pyinstaller.org/en/v6.10.0/runtime-information.html#ld-library-path-libpath-considerations
+        #      https://github.com/yt-dlp/yt-dlp/issues/4573
         def _fix(key):
             orig = env.get(f'{key}_ORIG')
             if orig is None:
@@ -845,7 +849,7 @@ class Popen(subprocess.Popen):
     def __init__(self, args, *remaining, env=None, text=False, shell=False, **kwargs):
         if env is None:
             env = os.environ.copy()
-        self._fix_pyinstaller_ld_path(env)
+        self._fix_pyinstaller_issues(env)
 
         self.__text_mode = kwargs.get('encoding') or kwargs.get('errors') or text or kwargs.get('universal_newlines')
         if text is True: