[Bugfix] fskip of EliminateCommonSubexpr cannot always return false (#4620)
[Bugfix] fskip of EliminateCommonSubexpr cannot always return false (#4620)

* 'fskip' will not always return false

fskip returns false at the end of PackedFunc, discards return true in 'cast' case

* Update build_module.cc

Laurawly/tvm-1,dmlc/tvm,dmlc/tvm,tqchen/tvm,Laurawly/tvm-1,sxjscience/tvm,dmlc/tvm,sxjscience/tvm,dmlc/tvm,dmlc/tvm,tqchen/tvm,tqchen/tvm,Laurawly/tvm-1,tqchen/tvm,sxjscience/tvm,sxjscience/tvm,tqchen/tvm,sxjscience/tvm,sxjscience/tvm,sxjscience/tvm,tqchen/tvm,tqchen/tvm,sxjscience/tvm,tqchen/tvm,sxjscience/tvm,Laurawly/tvm-1,Laurawly/tvm-1,Laurawly/tvm-1,dmlc/tvm,dmlc/tvm,tqchen/tvm,Laurawly/tvm-1,Laurawly/tvm-1,tqchen/tvm,Laurawly/tvm-1,dmlc/tvm,dmlc/tvm,Laurawly/tvm-1