Set icon and server env paths for meson devenv

This allows users to compile and run the project in a dev environment.

    meson setup x
    meson compile -C x
    meson devenv -C x
    scrcpy

This is an alternative to `./run x`.

PR #5658 <https://github.com/Genymobile/scrcpy/pull/5658>

Signed-off-by: Romain Vimont <rom@rom1v.com>