WIP: _v2-entry-point: Add support for STEAM_COMPAT_FLAGS
Recently the Steam client started to use the environment variable "STEAM_COMPAT_FLAGS" to set flags that the game we are about to launch requires.
Currently the only available flag is "search-cwd", to signal the lagacy behaviour where the game expects to have its installation path inside the "LD_LIBRARY_PATH".
This change requires a release of pressure-vessel that includes steam-runtime-tools!206 (merged)