MAIN_MODULE without EXPORT_ALL does not export js library functions

[kripken]

See for example the testcase added in #9698 - we need EXPORT_ALL there so that the side module can call cxa_throw, which is a JS library function.

It shouldn't be an observable difference if a function is from the JS library or not, so it should be exported like the compiled library code is, probably. I'm not sure of the ramifications of flipping EXPORT_ALL to 1 when MAIN_MODULE, though, so maybe we need something more specific?

[kripken]

Oh, this does look like a difference between the backends. Fastcomp doesn't export them, but it does add them to asmLibraryArg which is then imported into all wasm modules as env. So this is a regression on upstream. I'll open a PR.

[sbc100]

Does EXPORT_ALL effect JS functions? I thought it was for native functions. The docs for EXPORT_ALL are not clear to me.

It looks like you explicitly changes the behaviour in 1.38.16 such the EXPORT_ALL was not long enabled for MAIN_MODULES.