Expose emptyCache() function for nodejs+HMR support

[oguimbal]

When using cheap-module-eval-source-map or equivalent in Webpack, the sourcemap is embbeded in the eval() statement generated by Webpack... thus, source-map-support cannot access the actual source and perform the mapping.

... and given that i'm using HMR on my nodejs server which is a huge codebase, using source-map is not an option if I dont want to wait forever on each file change.

Thus, I've developped for myself a small webpack plugin that mitigates this issue. But it requires source-map-support to expose an emptyCache() method.

[timleslie]

@LinusU Any chance of this PR making it into the next release? I'm currently facing a problem where a part of the my system that I don't have control over is generating a lot of source maps that are blowing out my memory usage. Having a simple way to clear the cache would be a neat solve for my use case. Thanks 🙏

Update: I've found a different workaround for my use case 👍