Many informal observations of the WebGL build time, in particular the final linker step now take longer than when we first moved to Emscripten 2 in Unity 2021.2

This is especially detrimental in our user's iteration time with development (debug) builds.

The change which likely caused this was the upgrade to Emscripten 3.1.8 in Unity 2022.2

Brendan found this issue, https://github.com/emscripten-core/emscripten/issues/17019, that concluded compiling with "-sERROR_ON_WASM_CHANGES_AFTER_LINK -sWASM_BIGINT -O1" took linking time from 180 seconds to a couple seconds.

We set the linker options in Platforms/WebGL/WebGLPlayerBuildProgram/WebGLPlayerBuildProgram.cs
in the function SetupPlayerExecutable()
in particular the -O optimization flag is set on line 170

{code:java}
.WithOptLevel(!PlayerBuildConfig.Development && WebGlConfig.optimizeForSize ? "s" : "3")
{code}

We need to evaluate the linker flags used, particularly in our development builds to achieve the fastest link time possible, even at the expense of WASM size.

We should make sure that the release (non-development) builds remain with the optimal flags.