Clarify format of `-s` parameters in `emccArgs` in plugin-wasm options

[chrispcampbell]

In discussion thread #522, @serman noted an issue with passing -s parameters:

I managed to add the -S ASSERTIONS=1 to the wasm plugin:

wasmPlugin({ 
emccArgs: [
"-Wall", "-Os ", 
"-sSTRICT=1 ",
 "-sMALLOC=emmalloc", 
"-sFILESYSTEM=0 ",
 "-sMODULARIZE=1 ",
 "-sSINGLE_FILE=1 ", 
"-sEXPORT_ES6=1 ",
 "-sUSE_ES6_IMPORT_META=0 ", 
"-sENVIRONMENT='web,webview,worker' ", 
"-sEXPORTED_FUNCTIONS='_malloc','_free','_getInitialTime','_getFinalTime','_getSaveper','_setLookup','_runModelWithBuffers']", 
"-sEXPORTED_RUNTIME_METHODS=['cwrap']",
 "-sASSERTIONS=1"] }),

(note: I recommend including an example of this in the documentation since I didn't know that -s params don't have a space between "-s XXXXPARAMXXX" I can add it if you want)

It's interesting that in many of the Emscripten error messages, they show -s arguments with a space, and historically in SDE we have used a space as well, but it looks like the Emscripten documentation was amended at some point to recommend NOT including a space: https://emscripten.org/docs/tools_reference/emcc.html

Options can be specified as a single argument with or without a space between the -s and option name. e.g. -sFOO or -s FOO. It’s highly recommended you use the notation without space.

[chrispcampbell]

The reason that I think Sergio had trouble with spaces is because the plugin-wasm docs show this:

emccArgs

Optional emccArgs: string[] | () => string[]

The array of additional arguments to pass to emcc. If undefined, the plugin will use the following default set of arguments, which are tuned for (and known to work with) Emscripten versions 2.0.34 and 3.1.46, among others.

  -Wall
  -Os
  -s STRICT=1
  -s MALLOC=emmalloc
  -s FILESYSTEM=0
  -s MODULARIZE=1
  -s SINGLE_FILE=1
  -s EXPORT_ES6=1
  -s USE_ES6_IMPORT_META=0
  -s ENVIRONMENT='web,webview,worker'
  -s EXPORTED_FUNCTIONS=['_malloc','_free','_getInitialTime','_getFinalTime','_getSaveper','_setLookup','_runModelWithBuffers']
  -s EXPORTED_RUNTIME_METHODS=['cwrap']

---

When you pass an array of options, the spaces can cause problems if they are included in the strings due to the way args are passed to spawn. The above docs imply that you'd pass it like this (which I'm assuming how Sergio passed them):

['-s STRICT=1', ...]

But in fact you have to do the -s part as a separate string, like this:

['-s', 'STRICT=1', ...]

Or just drop the space altogether as Sergio found, and as recommended in the emcc docs:

['-sSTRICT=1', ...]

So I think we can amend the docs and the implementation of plugin-wasm to omit the space for clarity.

[Saschl]

Really sorry about that comment. My account got compromised and posted this malicious link. Lessons leaned..