Increase compiler optimization when using target=release on iOS/Android

[Calinou]

This improves performance on projects exported in release mode on iOS and Android, at the cost of slightly increased binary sizes.

Note that this may not be safe to cherry-pick to 3.x on iOS (assuming the bug mentioned in godotengine/godot-proposals#1987 was fixed in the GDScript rewrite in master).

[m4gr3d]

The Android section looks good!

[akien-mga]

If it's the only change, it's keep the startswith and just do:

opt = "-O3" if env["target"] == "release" else "-O2"
env.Append(CCFLAGS=[opt, ...])
env.Append(LINKFLAGS=[opt])

BTW, it seems weird that -O3 gets passed as a link flag, that doesn't make much sense. It's probably ignored by Clang.

For size optimization, we could try -Oz on platforms that build with Clang.

All this will need thorough regression testing of course.

[Calinou]

For size optimization, we could try -Oz on platforms that build with Clang.

I'd probably make that a separate option (such as optimize=size_extra), as -Oz is more aggressive and can lose quite a lot of speed compared to -Os.

[akien-mga]

If it's the only change, it's keep the startswith and just do: [...]

WDYT about this change? Worth doing, or do you prefer to keep it as is?

[Calinou]

WDYT about this change? Worth doing, or do you prefer to keep it as is?

It looks more readable with your change, so I applied it 🙂

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 3.5.