Increasing the minimum supported node version to v16.20

[Sam Clegg]

Hi all,

I'm in the process of bumping the minimum supported node version for the emscripten compiler.  This means anyone wanting to run the compiler itself would need to have at least node v16.20 installed.  See https://github.com/emscripten-core/emscripten/pull/20551.

Note that this matches the version of node we currently ship the emsdk.

As part of this we will also be dropping support for generating output that can run on older node versions.  i.e. specifying a `-sMIN_NODE_VERSION` of less than 16.2 will no longer be possible.

Is anyone currently running emcc on such an older version of node, or targeting such as version with the generated code?

cheers,

sam