get wrong path when pathname is softlink directory

https://github.com/llvm/llvm-project/blob/fbd24677963abedf88b6dbed277764e955374dd8/lldb/source/Utility/FileSpec.cpp#L185

when we use a path which contains softlink directory and also a relative path, such as `/usr/local/compile/interface/../api/A.h`
it contains softlink direcoty `/usr/local/compile/interface` which link to `/root/compile/`

The code will remove dot, so file path will become `/usr/local/compile//api/A.h` which does not exist.
But the path we need is `/root/api/A.h`

Start by reading the referenced logic in lldb/source/Utility/FileSpec.cpp around line 185 and trace how relative components are handled when a directory is a symlink. Done means a path like /usr/local/compile/interface/../api/A.h resolves to the intended target rather than the nonexistent lexical path, with regression coverage added in the relevant LLDB tests.

Written by the indexing model from the issue text.