update: Add "UPDATE_DRYRUN" mode

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
mxe-conf.cmake: Workaround buggy windres rules

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
assimp: Update

Signed-off-by: Timothy Gu <timothygu99@gmail.com>