can't test sinv utility with one argument via ctest

[jbathegit]

The sinv utility can be called with either one argument or two. The first argument is always the BUFR file to be read, and the second one is optional containing the directory location of the master tables. If the user only passes in one argument, then the utility defaults to the directory location of the master tables when the library was installed.

The problem is that, when doing a build, we always run "ctest" before we run "make install", and the latter step is where the master tables actually get installed into their default directory location, so they're not available there when "ctest" is run, and therefore we can't test calling the sinv utility with only one argument in test/testscripts/test_sinv.sh. I've noted this in a comment in that script, and for now it means we won't be able to achieve 100% gcovr testing coverage of the sinv source code.

BTW, and once "make install" is run, then the sinv utility can be called with just one argument and it works correctly. Again, we just can't include this as a test case when we run "ctest", since the "make install" hasn't occurred yet.