Add a compatibility shim for migrating Android build tools to Platforms

[freakboy3742]

Following the pattern used by the iOS build, adds a compatibility shim so that the buildbot will runPlatforms/Android, but that location will work on 3.13 and 3.14 repos that store the Android build code in Android/android.py.

Also updates the iOS configuration to use the same general pattern for invoking the build script.

As part of this, the CACHE_DIR configuration has been moved out of the buildbot definition, and into the environment where the buildbot is executed. This means the buildbot configuration is no longer sensitive to the specific user account that is hosting the buildbot instance.

This configuration can be landed now, without the Platforms migration having been made - the Android folder exists in all 3.13+ repos as of right now. Once the Platforms migration occurs the symlink step will become a no-op.

[vstinner]

On Python 3.13, this command fails with:

ln: failed to create symbolic link 'Platforms/Android': No such file or directory

You should create the Platforms/ directory somehow. For example, add [ -e Platforms ] || mkdir Platforms; prefix to your command.

[freakboy3742]

🤦 I forgot that 3.14 has the Platforms directory; but 3.13 doesn't. Fixed.

[vstinner]

For readability, you should add spaces:

Suggested change

	"[ -e Platforms/Android ]"
	"|| ln -s ../Android Platforms/Android"
	"&& ln -si ../Android/android.py Platforms/Android/__main__.py"
	"[ -e Platforms/Android ]"
	"|| ln -s ../Android Platforms/Android"
	"&& ln -si ../Android/android.py Platforms/Android/__main__.py"

[vstinner]

LGTM