ci: enable VOXL2 CI builds with private Docker container

Remove modalai_voxl2 and qurt from CI exclusion lists and add
container overrides to use the private ghcr.io/px4/px4-dev-voxl2
image which contains the Qualcomm Hexagon SDK.

- Add voxl2 build group with x64 runner for cross-compilation
- Add GHCR credentials to workflow for private container pull
- Add packages:read permission to workflow
- Auto-build libfc_sensor.so stub during cmake configure
- Handle missing .px4/.elf gracefully in artifact packaging

Signed-off-by: Ramon Roche <mrpollo@gmail.com>

boards/modalai/voxl2/cmake/init.cmake

@@ -32,3 +32,19 @@
 ############################################################################
 
 include_directories(${PX4_BOARD_DIR}/libfc-sensor-api/inc)
+
+# Build libfc_sensor.so stub library automatically if not already built
+set(FC_SENSOR_LIB ${PX4_BOARD_DIR}/libfc-sensor-api/build/libfc_sensor.so)
+if(NOT EXISTS ${FC_SENSOR_LIB})
+	execute_process(
+		COMMAND ${CMAKE_COMMAND} -E make_directory ${PX4_BOARD_DIR}/libfc-sensor-api/build
+	)
+	execute_process(
+		COMMAND ${CMAKE_COMMAND} -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER} ..
+		WORKING_DIRECTORY ${PX4_BOARD_DIR}/libfc-sensor-api/build
+	)
+	execute_process(
+		COMMAND ${CMAKE_COMMAND} --build .
+		WORKING_DIRECTORY ${PX4_BOARD_DIR}/libfc-sensor-api/build
+	)
+endif()