mpy_cross: Cache it in the user cache path

.. rather than in a build_deps folder, polluting the repo where it's used

this also enables sharing the copy of mpy-cross across multiple repos.

circuitpython_build_tools/scripts/build_bundles.py

@@ -32,6 +32,7 @@
 import zipfile
 
 import click
+import platformdirs
 
 from circuitpython_build_tools import build
 from circuitpython_build_tools import target_versions
@@ -41,6 +42,7 @@
 else:
     import importlib.metadata as importlib_metadata
 
+mpy_cross_path = platformdirs.user_cache_path("circuitpython-build-tools", ensure_exists=True)
 
 BLINKA_LIBRARIES = [
     "adafruit-blinka",
@@ -282,7 +284,7 @@ def build_bundles(filename_prefix, output_directory, library_location, library_d
     if "mpy" not in ignore:
         os.makedirs("build_deps", exist_ok=True)
         for version in target_versions.VERSIONS:
-            mpy_cross = "build_deps/mpy-cross-" + version["name"] + (".exe" * (os.name == "nt"))
+            mpy_cross = mpy_cross_path / ("mpy-cross-" + version["name"] + (".exe" * (os.name == "nt")))
             build.mpy_cross(mpy_cross, version["tag"])
             zip_filename = os.path.join(output_directory,
                 filename_prefix + '-{TAG}-mpy-{VERSION}.zip'.format(

requirements.txt

@@ -3,3 +3,4 @@ requests
 semver
 wheel
 tomli; python_version < "3.11"
+platformdirs

setup.py

@@ -14,7 +14,7 @@
       package_data={'circuitpython_build_tools': ['data/mpy-cross-*']},
       zip_safe=False,
       python_requires='>=3.10',
-      install_requires=['Click', 'requests', 'semver', 'tomli; python_version < "3.11"'],
+      install_requires=['Click', 'requests', 'semver', 'tomli; python_version < "3.11"', 'platformdirs'],
       entry_points='''
         [console_scripts]
         circuitpython-build-bundles=circuitpython_build_tools.scripts.build_bundles:build_bundles