building: use os.makedirs(exist_ok=True) when creating directories

When creating parent directory structure for collected files
in COLLECT and BUNDLE, avoid explicitly checking whether the
directory already exists. Instead, call `os.makedirs` with
`exists_ok=True` and catch the `FileExistsError`.

PyInstaller/building/api.py

@@ -964,9 +964,9 @@ def assemble(self):
             # Create parent directory structure, if necessary
             dest_path = os.path.join(self.name, dest_name)  # Absolute destination path
             dest_dir = os.path.dirname(dest_path)
-            if not os.path.exists(dest_dir):
-                os.makedirs(dest_dir)
-            elif not os.path.isdir(dest_dir):
+            try:
+                os.makedirs(dest_dir, exist_ok=True)
+            except FileExistsError:
                 raise SystemExit(
                     f"Pyinstaller needs to create a directory at {dest_dir!r}, "
                     "but there already exists a file at that path!"

PyInstaller/building/osx.py

@@ -608,9 +608,9 @@ def assemble(self):
             # Create parent directory structure, if necessary
             dest_path = os.path.join(self.name, dest_name)  # Absolute destination path
             dest_dir = os.path.dirname(dest_path)
-            if not os.path.exists(dest_dir):
-                os.makedirs(dest_dir)
-            elif not os.path.isdir(dest_dir):
+            try:
+                os.makedirs(dest_dir, exist_ok=True)
+            except FileExistsError:
                 raise SystemExit(
                     f"Pyinstaller needs to create a directory at {dest_dir!r}, "
                     "but there already exists a file at that path!"