Add some compile options, add vulkan dependency export (#2062)
* vulkan cmake export templete
* 1) vulkan cmake dependency export. 2) support opencv_world import. 3) add BUILD_WITH_STATIC_CRT option
* Threads dependency
* NCNN_BUILD_WITH_STATIC_CRT option
* we do not support cmake before version 3.15 for option NCNN_BUILD_WITH_STATIC_CRT