Wasm: Fix mono patch application on Emscripten 1.38.47

[akien-mga]

As a reminder, we pinned the Emscripten version to 1.38.47-upstream as we had a regression with wasm generation in 1.38.48 and 1.39.x back in 17666f0.

This patch comes from Mono's 2019-10 branch (6.8.x): mono/mono#17094
(Slightly amended to include a version bump in wasm.mk that should have been done by other intermediate patches.)

We might need a recent Emscripten 1.39.x in the 3.2 branch eventually (CC @Faless), so we might have to consider upgrading to a newer Mono branch with support for a more recent Emscripten.

[akien-mga]

For the record, this patch application failure should also have affected previous container builds used in Godot 3.2 and 3.2.1. I did not notice it until now because of godotengine/godot-mono-builds/issues/6.

I don't know what impact it has on our 3.2 and 3.2.1 WebAssembly templates for C#.

[akien-mga]

We might need a recent Emscripten 1.39.x in the 3.2 branch eventually (CC @Faless), so we might have to consider upgrading to a newer Mono branch with support for a more recent Emscripten.

I had a quick check at the supported Emscripten version in different Mono branches (I think we can assume that the hardcoded Emscripten version in Mono's sdks/build/wasm.mk is the version we should use, as Emscripten breaks compat in every other patch release):

• Mono 2019-08 (6.6.x, our current branch): 1.38.38 (hence the two patches we carry along)
• Mono 2019-10 (6.8.x, current upstream stable): 1.38.47
• Mono 2019-12 (6.10.x, current upstream preview): 1.39.3
• Mono 2020-02 (6.12.x, current upstream nightly): 1.39.7

Latest emscripten today is 1.39.11.

So yeah, we should make sure that our Wasm port does not expect cutting edge Emscripten versions, unless we're willing to go with Mono Nightly for our stable releases...

We could consider an upgrade to Mono 6.10.x once it hits stable though, which gives us Emscripten 1.39.3 support without hacks.

[akien-mga]

I confirm that the patches apply fine now when building a container against mono-6.6.0.166.