use BUILD_SHARED_LIBS to control whether a library is shared or static, make our bundled physfs library check for this configuration
foreach(dir
Art
Bamboo
Bath
Blox
Brick
Cake
Cave
Castle
Cheese
Christmas
City
Compost
CrazyMission
Deepspace
Desert
EarthRise
Eyes
Freeway
Fruit
Golf
Halloween
Hell
Island
Jungle
Nature
Olympics
Planes
Sheep
Snow
Stage
Underwater
)
add_subdirectory(${dir})
endforeach(dir)