Web builds are no longer built with `-Os` by default

Tested versions

Reproducible in 4.3.beta (ec02d406ca0b9c822addff49cf58e9a72cf74eb0)

System information

Fedora Linux 40 (KDE Plasma) - Wayland - Vulkan (Forward+) - dedicated AMD Radeon RX 7600M XT (RADV NAVI33) - AMD Ryzen 7 7840HS w/ Radeon 780M Graphics (16 Threads)

Issue description

When building for Web with scons p=web target=template_release verbose=yes, you should see it use -Os as optimization, which is set as custom value for env["optimize"] in platform/web/detect.py.

But I broke it with one of my PRs in 4.3 (likely #91791) so now this override is no longer respected and instead this code in SConstruct forces it to speed (which is the default on other platforms for release templates).

if env.dev_build:
    opt_level = "none"
elif env.debug_features:
    opt_level = "speed_trace"
else:  # Release
    opt_level = "speed"

env["optimize"] = ARGUMENTS.get("optimize", opt_level)

ARGUMENTS only includes command line arguments, not overrides taken from detect.py.

One potential solution would be to add a auto mode for optimize, and only do this magic if it's auto.

Steps to reproduce

scons p=web target=template_release verbose=yes

Minimal reproduction project (MRP)

n/a

godotengine / godot