Issue 5411: Out of memory error in emscripten builds

[aglitchman]

This pull request fixes the issue #5411 for Defold 1.2.178 (beta) which uses the latest Emscripten 2.0.11.

Detailed description

Starting from 2.0.10 the WebAssembly memory used by Emscripten programs is, by default, created in the wasm file and exported to JavaScript, and wasm ignores the value of Module.INITIAL_MEMORY. The IMPORTED_MEMORY=1 setting can be used to revert to the old behaviour. But, you can't set the heap size for wasm in runtime because the max memory size is baked into the wasm binary. The only way to fix that is to add the settings IMPORTED_MEMORY=1 and ALLOW_MEMORY_GROWTH=1 for wasm builds.

Asm.js runs well as before and it uses the value of Module.INITIAL_MEMORY for heap size because TOTAL_MEMORY was renamed to INITIAL_MEMORY some time ago.

And the value of Module.INITIAL_MEMORY should be set before loading of runtime (it's due to changes by #5211).

[JCash]

Looks good.
Only thing missing is the corresponding change in waf_dynamo.py (would be nice to have it all in the same PR)

[JCash]

Looks good!

[aglitchman]

@JCash I have been testing those new settings for HTML5 builds, and I have just found out that I can't set heap size for wasm in runtime less than 256MB. The error is:
wasm instantiation failed! LinkError: WebAssembly.instantiate(): memory import 384 is smaller than initial 4096, got 2048

Could you please test this case too?

The build option -s INITIAL_MEMORY=... should be set to the minimal value (32MB or something like that). Because I know that @AGulev sets the heap size for his games much lower than 256MB. And I do that, too.