Understand paths in `-open` in `bsc-flags`

[cristianoc]

E.g. "-open ReScriptJs.Js" is not recognised
while "-open ReScriptJs", "-open Js" is

[cristianoc]

CC @zth

[cristianoc]

The semantics of "-open ReScriptJs", "-open Js" is not the same as "-open ReScriptJs.Js". To be accurate, this should be taken into account.

So this issue is not completely fixed yet.

[zth]

This is now fixed.