treewide: Fix unsafe concatenation of $LD_LIBRARY_PATH

Naive concatenation of $LD_LIBRARY_PATH can result in an empty
colon-delimited segment; this tells glibc to load libraries from the
current directory, which is definitely wrong, and may be a security
vulnerability if the current directory is untrusted.  (See #67234, for
example.)  Fix this throughout the tree.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

pkgs/development/libraries/criterion/default.nix

@@ -30,7 +30,7 @@ stdenv.mkDerivation rec {
   cmakeFlags = [ "-DCTESTS=ON" ];
   doCheck = true;
   preCheck = ''
-    export LD_LIBRARY_PATH=`pwd`:$LD_LIBRARY_PATH
+    export LD_LIBRARY_PATH=`pwd`''${LD_LIBRARY_PATH:+:}$LD_LIBRARY_PATH
   '';
   checkTarget = "criterion_tests test";