Do not clear the current LD_PRELOAD_PATH

doc/Ecosystem.md

@@ -75,7 +75,7 @@ You will need to pin the specific toolchain version used, by setting the `"rust-
 
 For RLS to work, `vscode` need a path to the `rls-preview` library (using the environment variable `LD_LIBRARY_PATH` (Linux), `DYLD_LIBRARY_PATH` (OSX ?)). 
 ```
-export LD_LIBRARY_PATH=$(rustc --print sysroot)/lib
+export LD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$LD_LIBRARY_PATH
 ```
 You may add this to your `~/.bash_profile`, and start vscode (`code` is the name of the executable) in a new terminal (to ensure that the `LD_LIBRARY_PATH` (Linux) `DYLD_LIBRARY_PATH` (OSX?) is correctly set). If `code` is run from your window manager (e.g., `plasma`), make sure that the environment is set correctly.