Reconsider dynamic library loading strategy

[apache]

Reconsider dynamic library loading strategy

[tqchen]

I agree that a search algorithm that searches the following priority makes sense

• LD_LIBRARY_PATH
• inplace
• installation location (possible cmake path, we don't have to ask cmake to dump to lib)

Having the LD_LIBRARY_PATH as highest priority enables configurability by allowing user to simply set it before importing tvm to point to different versions.
We could also have an environment variable TVM_LIBRARY_PATH, which have the highest priority, to allow python script to quickly change the path by setting this variable

[tqchen]

As for make system, for now i think we can keep the makefile. In general i favor cmake on complicated builds, but makefile offers some flexiblity in terms minimum dependency and when building rules are very simple, like build runtime on a dev board which may not have right version of cmake available