[mono][wasm]Avoid passing -emit-llvm to emcc when compiling AOT images

[vargaz]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

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Issue Details

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Description

Configuration

Regression?

Other information

Author:	vargaz
Assignees:	-
Labels:	arch-wasm, untriaged
Milestone:	-