SCons: Add only selected platform's opts to env

Otherwise we can get situations where platform-specific opts with the same name
can override each other depending on the order at which platforms are parsed,
as was the case with `use_static_cpp` in Linux/Windows.

Fixes #44304.

This also has the added benefit that the `scons --help` output will now only
include the options which are relevant for the selected (or detected) platform.

0 files changed, 0 insertions, 0 deletions