KWSys: Remove realpath from SystemTools::GetPath (#10335)

Commit "merge in changes for beos support" (2006-12-04) added a realpath
call for every directory parsed out of a PATH-style environment
variable.  No reason was given in the commit message or comments.

The call incorrectly resolves symlinks in referenced paths.  Remove it.
If BeOS support really needs it then it can be restored for that
platform with a full explanation.