separateDebugInfo: Assert Linux

Also remove some unintended setting of separateDebugInfo.

pkgs/applications/misc/hello/ex-2/default.nix

···
 
   doCheck = false;
 
-  separateDebugInfo = true;
-
   meta = {
     description = "A program that produces a familiar, friendly greeting";
     longDescription = ''

pkgs/build-support/setup-hooks/separate-debug-info.sh

···
         # Skip non-ELF files.
         exec 10< "$i"
         read -n 4 -u 10 magic
-        if [[ "$magic" =~ ELF ]]; then echo FOO; fi
         exec 10<&-
 
         # Extract the Build ID. FIXME: there's probably a cleaner way.

pkgs/stdenv/generic/default.nix

···
 
       outputs' =
         outputs ++
-        (if separateDebugInfo then [ "debug" ] else []);
+        (if separateDebugInfo then assert result.isLinux; [ "debug" ] else []);
 
       buildInputs' = buildInputs ++
         (if separateDebugInfo then [ ../../build-support/setup-hooks/separate-debug-info.sh ] else []);

pkgs/tools/package-management/nix/default.nix

···
 
     doInstallCheck = false;
 
-    separateDebugInfo = true;
-
     crossAttrs = {
       postUnpack =
         '' export CPATH="${bzip2.crossDrv}/include"