jre_minimal package does not strip libjvm.so by default to make package size smaller

[vroad]

Describe the bug
jre_minimal package does not strip jlink result file. It should strip libjvm.so by default to save disk space.
If I run strip -p --strip-unneeded ./lib/server/libjvm.so, the size goes down to 17.5MB from 232.6MB.

To Reproduce
Steps to reproduce the behavior:

Create some derivation that uses jre_minimal. jre_minimal will create libjvm.so using jlink, though it doesn't strip the binary at all.

{ jre, stdenv }:
stdenv.mkDerivation {
  # other configs...
  installPhase = ''
    # other scripts...
    wrapProgram "$out/bin/my-app" \
      --set JAVA_HOME "${jre.home}"
  '';
}

let
  sources = import ./sources.nix;
  pkgs = import sources.nixpkgs { };
  jre = pkgs.jre_minimal.override {
    modules = [
      "java.base"
    ];
    jdk = pkgs.jdk11_headless;
  };
  myApp = pkgs.callPackage ./my-app.nix {
    inherit jre;
  };
in
myApp

Expected behavior
jre_minimal strip the binary by default to make libjvm.so smaller.

Additional context
Related GitHub issue: docker-library/openjdk#217
Related NixOS discourse discussion: https://discourse.nixos.org/t/how-to-create-a-docker-image-with-minimal-jdk-11-there-is-no-jre11-headless/11849/8

I don't know how strip works. What's the difference between --strip-unneeded and --strip-debug? Which one is better in this case?

Notify maintainers

@raboof
@roberth

Metadata
Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

 - system: `"x86_64-linux"`
 - host os: `Linux 4.19.121-linuxkit, Alpine Linux, noversion`
 - multi-user?: `yes`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.3.10`
 - channels(root): `"nixpkgs-21.05pre273941.a2b0ea6865b"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixpkgs`

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/how-to-create-a-docker-image-with-minimal-jdk-11-there-is-no-jre11-headless/11849/10