cc-wrapper, bintools-wrapper: Remove now unneeded set {+,-}u

pkgs/build-support/bintools-wrapper/default.nix

@@ -199,11 +199,7 @@ stdenv.mkDerivation {
   ];
 
   postFixup =
-    ''
-      set -u
-    ''
-
-    + optionalString (libc != null) (''
+    optionalString (libc != null) (''
       ##
       ## General libc support
       ##

pkgs/build-support/bintools-wrapper/setup-hook.sh

@@ -2,8 +2,6 @@
 #
 # See comments in cc-wrapper's setup hook. This works exactly the same way.
 
-set -u
-
 # Skip setup hook if we're neither a build-time dep, nor, temporarily, doing a
 # native compile.
 #
@@ -73,4 +71,3 @@ export NIX_HARDENING_ENABLE
 
 # No local scope in sourced file
 unset -v role_pre role_post cmd upper_case
-set +u