Merely assigning environment variables is insufficient for setting up
dev environment now. We need to run pip to install hidet package in
develop mode.

Users still need to build source files written in C++ manually. Consider
integrating that into `setup.py` in the future?

)

Previously, if a primitive function calls a primitive function, the
`instantiate_symbols` pass will update the corresponding
`hidet.ir.primitives.func.PrimitiveFunctionRegistry.function` in-place
(I am not sure exactly how it's done, but this is what I observed),
adding symbol variables to its parameters. The primitive function pool
is a global variable, therefore this effect is cumulative across tuning
candidates. So while candidate 0 will have no problem, candidate 1 will
have two extra copies of symbol params, and so on, leading to compile
errors.

Since primitive functions do not need symbol vars, a quick fix is just
to not instantiate any symbols for them.