cmake - check directory existence before copy_directory (#10402)

Starting with cmake version 3.12 the cmake -E copy_directory
command fails if the source directory does not exist. This results
in a build failure. This fix creates the source directory before
the copy which does not harm if the source directory exists.

Closes: #10368

ROMFS/CMakeLists.txt

@@ -105,6 +105,7 @@ endif()
 
 add_custom_command(OUTPUT romfs_extras.stamp
 	COMMAND ${CMAKE_COMMAND} -E make_directory ${romfs_gen_root_dir}/extras/
+	COMMAND ${CMAKE_COMMAND} -E make_directory ${PX4_BINARY_DIR}/romfs_extras/
 	COMMAND ${CMAKE_COMMAND} -E copy_directory ${PX4_BINARY_DIR}/romfs_extras/ ${romfs_gen_root_dir}/extras/
 	COMMAND ${CMAKE_COMMAND} -E touch romfs_extras.stamp
 	DEPENDS