If you know only that the library will be in the same folder as the script, but don't know the fully-qualified location of the script and library, then you'll have to use something like the approach that
showed us.
By the way, in the example you gave in your original post, the actual working directory (from Inline's point of view) was C:\test\_Inline\build\test_pl_0ca9. The "\test\_Inline\build\" part is known in advance, and you can even configure things so that "test\_Inline" is replaced by the location of your choice. The "test_pl_0ca9" could also be determined in advance - but it will change everytime you make a change to the C code in the script.