HTML5: Fix support for Emscripten 1.39.1+
HTML5: Fix support for Emscripten 1.39.1+

A change in upstream Emscripten 1.39.1+ made our buildsystem error
out where it was previously only issuing a warning:
```
[  5%] Linking Static Library ==> main/libmain.javascript.opt.bc
shared:WARNING: Assuming object file output in the absence of `-c`, based on output filename. Please add with `-c` or `-r` to avoid this warning
Ranlib Library         ==> main/libmain.javascript.opt.bc
/opt/emsdk/upstream/bin/llvm-ranlib: error: unable to load 'main/libmain.javascript.opt.bc': file too small to be an archive
```

As advised on emscripten-core/emscripten#9806, we should be using
`emar` here to create the static library and not `emcc`.
This was apparently done to workaround Emscripten issues in the past,
but evidently this is no longer necessary.

The rest of the `env` redefinitions should probably be re-assessed
against the current state of Emscripten.

Fixes #33374.

guilhermefelipecgs/godot,Faless/godot,josempans/godot,vnen/godot,firefly2442/godot,firefly2442/godot,Faless/godot,MarianoGnu/godot,honix/godot,BastiaanOlij/godot,Paulloz/godot,Zylann/godot,pkowal1982/godot,josempans/godot,honix/godot,DmitriySalnikov/godot,sanikoyes/godot,ZuBsPaCe/godot,honix/godot,guilhermefelipecgs/godot,guilhermefelipecgs/godot,Paulloz/godot,Valentactive/godot,josempans/godot,ex/godot,vnen/godot,godotengine/godot,sanikoyes/godot,Zylann/godot,Zylann/godot,Shockblast/godot,firefly2442/godot,ex/godot,ZuBsPaCe/godot,Valentactive/godot,ex/godot,Valentactive/godot,godotengine/godot,sanikoyes/godot,ex/godot,vnen/godot,Faless/godot,firefly2442/godot,firefly2442/godot,Faless/godot,Shockblast/godot,vkbsb/godot,ZuBsPaCe/godot,akien-mga/godot,vkbsb/godot,DmitriySalnikov/godot,DmitriySalnikov/godot,godotengine/godot,DmitriySalnikov/godot,Zylann/godot,ex/godot,Shockblast/godot,akien-mga/godot,MarianoGnu/godot,josempans/godot,pkowal1982/godot,guilhermefelipecgs/godot,sanikoyes/godot,BastiaanOlij/godot,vkbsb/godot,ex/godot,MarianoGnu/godot,ex/godot,Shockblast/godot,Zylann/godot,Shockblast/godot,ZuBsPaCe/godot,Shockblast/godot,Shockblast/godot,guilhermefelipecgs/godot,MarianoGnu/godot,Faless/godot,pkowal1982/godot,Zylann/godot,josempans/godot,BastiaanOlij/godot,pkowal1982/godot,pkowal1982/godot,BastiaanOlij/godot,vkbsb/godot,firefly2442/godot,firefly2442/godot,ZuBsPaCe/godot,Zylann/godot,ZuBsPaCe/godot,akien-mga/godot,Paulloz/godot,vnen/godot,firefly2442/godot,Paulloz/godot,honix/godot,godotengine/godot,Valentactive/godot,josempans/godot,Shockblast/godot,Faless/godot,guilhermefelipecgs/godot,BastiaanOlij/godot,Valentactive/godot,josempans/godot,DmitriySalnikov/godot,godotengine/godot,Valentactive/godot,Faless/godot,honix/godot,ex/godot,DmitriySalnikov/godot,Paulloz/godot,MarianoGnu/godot,BastiaanOlij/godot,vnen/godot,sanikoyes/godot,Paulloz/godot,vnen/godot,godotengine/godot,Faless/godot,vnen/godot,akien-mga/godot,Paulloz/godot,pkowal1982/godot,MarianoGnu/godot,vkbsb/godot,sanikoyes/godot,vkbsb/godot,josempans/godot,guilhermefelipecgs/godot,vkbsb/godot,pkowal1982/godot,pkowal1982/godot,Valentactive/godot,MarianoGnu/godot,MarianoGnu/godot,BastiaanOlij/godot,akien-mga/godot,sanikoyes/godot,BastiaanOlij/godot,akien-mga/godot,akien-mga/godot,guilhermefelipecgs/godot,vnen/godot,honix/godot,vkbsb/godot,godotengine/godot,sanikoyes/godot,akien-mga/godot,DmitriySalnikov/godot,Zylann/godot,ZuBsPaCe/godot,ZuBsPaCe/godot,Valentactive/godot,godotengine/godot