JS: Re-enable LTO for classical builds

I had done this locally already but somehow forgot to commit and lost the changes,
so re-doing.

Not enabling it for Mono builds as it causes errors (or crashes with threads enabled)
with Emscripten 1.39.9.

Author: akien-mga

build-javascript/build.sh

@@ -6,8 +6,8 @@ set -e
 
 export BUILD_NAME=official
 export SCONS="scons -j${NUM_CORES} verbose=yes warnings=no progress=no"
-export OPTIONS="debug_symbols=no use_lto=no"
-export OPTIONS_MONO="module_mono_enabled=yes mono_static=yes mono_prefix=/root/mono-installs/wasm-runtime-release"
+export OPTIONS="debug_symbols=no use_lto=yes"
+export OPTIONS_MONO="module_mono_enabled=yes mono_static=yes mono_prefix=/root/mono-installs/wasm-runtime-release use_lto=no"
 export TERM=xterm
 
 rm -rf godot