[Silabs] fix non SLC build script (#25926)

* Added avariable to let the script use the venv python when not using SLC

* Restyled by shellharden

* Restyled by shfmt

* moved the PYTHON_PATH to be after activate.sh

* Restyled by shfmt

---------

Co-authored-by: Restyled.io <commits@restyled.io>

scripts/examples/gn_efr32_example.sh

@@ -268,12 +268,16 @@ else
  } &>/dev/null
  fi
 
- if [ "$USE_SLC" == true ] && [ "$GN_PATH_PROVIDED" == false ]; then
- GN_PATH=./.environment/cipd/packages/pigweed/gn
+ if [ "$USE_SLC" == true ]; then
+ PYTHON_PATH="/usr/bin/python3"
+ if [ "$GN_PATH_PROVIDED" == false ]; then
+ GN_PATH=./.environment/cipd/packages/pigweed/gn
+ fi
  elif [ "$USE_SLC" == false ]; then
  # Activation needs to be after SLC generation which is done in gn gen.
  # Zap generation requires activation and is done in the build phase
  source "$CHIP_ROOT/scripts/activate.sh"
+ PYTHON_PATH=$VIRTUAL_ENV"/bin/python3"
  fi
 
  BUILD_DIR=$OUTDIR/$SILABS_BOARD
@@ -296,9 +300,9 @@ else
  fi
 
  if [ -z "$optArgs" ]; then
- "$GN_PATH" gen --check --script-executable="/usr/bin/python3" --root="$ROOT" --args="silabs_board=\"$SILABS_BOARD\"" "$BUILD_DIR"
+ "$GN_PATH" gen --check --script-executable="$PYTHON_PATH" --fail-on-unused-args --export-compile-commands --root="$ROOT" --args="silabs_board=\"$SILABS_BOARD\"" "$BUILD_DIR"
  else
- "$GN_PATH" gen --check --script-executable="/usr/bin/python3" --root="$ROOT" --args="silabs_board=\"$SILABS_BOARD\" $optArgs" "$BUILD_DIR"
+ "$GN_PATH" gen --check --script-executable="$PYTHON_PATH" --fail-on-unused-args --export-compile-commands --root="$ROOT" --args="silabs_board=\"$SILABS_BOARD\" $optArgs" "$BUILD_DIR"
  fi
  fi