test: fix running 'small' lib tests for OOS build

The 'small' lib test suite was not run for out-of-source builds since
the wrong symlink was created for test binaries and test-run couldn't
find them. Now it is fixed.

When test-run loads tests, first, it searches the suite.ini file and if
it exists test-run consider the dir as a test suite. So there was sense
to create a permanent link for 'small' lib tests.

Closes #4485

NO_DOC=testing stuff
NO_TEST=testing stuff
NO_CHANGELOG=testing stuff