use BUILD_SHARED_LIBS to control whether a library is shared or static, make our bundled physfs library check for this configuration
if(WIN32 AND NOT UNIX)
file(GLOB DLLs *.dll)
file(GLOB ICOs *.ico)
install(FILES
${DLLs}
${ICOs}
DESTINATION ${target_library_install_dir})
endif(WIN32 AND NOT UNIX)