makeBinaryWrapper.extractCmd: fix use in cross compilation

pkgs/build-support/setup-hooks/make-binary-wrapper/default.nix

···
   passthru = {
     # Extract the function call used to create a binary wrapper from its embedded docstring
     extractCmd = writeShellScript "extract-binary-wrapper-cmd" ''
-      strings -dw "$1" | sed -n '/^makeCWrapper/,/^$/ p'
+      ${cc.bintools.targetPrefix}strings -dw "$1" | sed -n '/^makeCWrapper/,/^$/ p'
     '';
 
     tests = tests.makeBinaryWrapper;