Ada: Remove libutil dependency on Linux.
The Ada compiler removes the dependency on libutil when targeting Linux.
The Ada runtime no longer depends on libutil when targeting Linux. This synchronizes the GPR build with the Makefile build, where the dependency was already absent. Since libutil is often empty on Linux, this simplifies the dependencies.
In Details
This commit modifies s-oscons-tmplt.c to remove the Ada runtime's dependency on libutil for Linux targets. The PTY_Library is now defined as empty for Linux. This change aligns the GPR build with the Makefile build, where libutil was not included due to its typically empty definition on Linux systems.
For Context
libutil is a library that provides various utility functions. On Linux systems, this library is often empty or contains very few functions. This commit removes an unnecessary dependency on libutil for the Ada runtime when targeting Linux. This can simplify the build process and reduce the overall size of the compiled code.