Fix leakage of transitive dependencies to dependent projects

[tudortimi]

Assuming we have 3 projects:

• bot, has no dependencies
• mid, has a dependency on bot
• top, has dependencies on both mid and bot

If top only defines a dependency on mid, it will still compile, because bot leaks into the compilation of top.

For Xcelium, it seems that the -pkgsearch option would help here. This explicitly forces us to specify where to look for packages. When compiling top, without specifying a dependency on bot, we would get the following:

-makelib top_lib
  -pkgsearch mid_lib
  top.sv
-endlib

This would cause a compile error related to bot not being visible.

This mechanism is only activated when there is at least one -pkgsearch directive. To ensure that we specify all required -pkgsearch options, even when forgetting all dependencies, we can add a dummy -pkgsearch option pointing to the current library.

[tudortimi]

We still have to check what happens where dependencies have internal dependencies, which we don't want to expose.

[tudortimi]

Exported headers also have to be fixed. Those we can fix in a simulator independent way.