LCC: Several fixes for MCST LCC testing on OS Elbrus

First, we sorted out the issue with !8665 (merged) ; it is because of broken libc in this version of OS Elbrus, that causes some tests to fail due to failed growth of procedure stack (IIRC, it was due to incorrect call of either brk() or mprotect() inside this version of libc). I specifically decided to disable tests causing such an issue, if that libc version is found.

And also, there's several minor fixes for issues I found in newly released OS Elbrus 8.0 (duplicate // in library path), in old LCC versions (that do not support C++20), and in special cases when ctest's build subdirectory is not as it supposed to be by default (to keep testing Fortran even on those LCC versions that do not handle long paths correctly).

Topic-rename: lcc-updates