[Converter:Refact] Allow disabling converters

[DavidVentura]

Description

Allows disabling specific converters for MNNConvert.
Need to migrate users of legacy ONNX models to MNN, without having them redownload everything

Module

Converter

Type

• Feature
• Bugfix
• Perf
• Refact
• Style
• Doc
• Test
• Chore

Checklist

• Commit message follows [Module:Type] Description format
• Code compiles without errors
• Tested on relevant platform(s)
• No unrelated format or style changes included

[wangzhaode]

Hi @DavidVentura, thanks for the contribution!

MNNConvert is an offline tool that doesn't ship to end-user devices, so binary size reduction isn't a concern for it. We'd prefer to keep the converter build system simple and don't plan to merge this.

If you have a specific need to slim down the converter binary, we'd suggest maintaining a local patch to strip out the converters you don't need.

Thanks again for the effort!