Fix intermittent anki/backend_pb2.py build error on Windows

The _pb2 files are built for both the host and target architectures
(which seems superfluous - we may be able to fix that in the future).
Our script wrote the files into the build folder and then moved them
into the correct place, but because builds are not sandboxed on Windows,
the two actions were racy, and could cause each other to fail. Solved
by writing the files directly into their target locations.

pylib/tools/protoc_wrapper.py

@@ -9,8 +9,10 @@ import os
 import shutil
 import subprocess
 import sys
+from pathlib import Path
 
 (protoc, mypy_protobuf, outdir, *protos) = sys.argv[1:]
+outpath = Path(outdir).parent
 
 if protos[0].startswith("external"):
     prefix = "external/ankidesktop/proto/"
@@ -22,8 +24,8 @@ subprocess.run(
     [
         protoc,
         f"--plugin=protoc-gen-mypy={mypy_protobuf}",
-        "--python_out=.",
-        "--mypy_out=.",
+        f"--python_out={outpath}",
+        f"--mypy_out={outpath}",
         f"-I{prefix}",
         f"-Iexternal/ankidesktop/{prefix}",
         *protos,
@@ -32,9 +34,3 @@ subprocess.run(
     stderr=subprocess.DEVNULL,
     check=True,
 )
-
-for proto in protos:
-    without_prefix_and_ext, _ = os.path.splitext(proto[len(prefix) :])
-    for ext in "_pb2.py", "_pb2.pyi":
-        path = without_prefix_and_ext + ext
-        shutil.move(path, os.path.join(outdir, os.path.basename(path)))