nixosTests.nixseparatedebuginfod: fix test

nix is not built with separateDebuginfo set to true anymore. Let's use
gnumake instead.

nixos/tests/nixseparatedebuginfod.nix

@@ -5,7 +5,7 @@ let
 in
 {
   name = "nixseparatedebuginfod";
-  # A binary cache with debug info and source for nix
+  # A binary cache with debug info and source for gnumake
   nodes.cache =
     { pkgs, ... }:
     {
@@ -15,8 +15,8 @@ in
         openFirewall = true;
       };
       system.extraDependencies = [
-        pkgs.nix.debug
-        pkgs.nix.src
+        pkgs.gnumake.debug
+        pkgs.gnumake.src
         pkgs.sl
       ];
     };
@@ -33,9 +33,10 @@ in
     environment.systemPackages = [
       pkgs.valgrind
       pkgs.gdb
+      pkgs.gnumake
       (pkgs.writeShellScriptBin "wait_for_indexation" ''
         set -x
-        while debuginfod-find debuginfo /run/current-system/sw/bin/nix |& grep 'File too large'; do
+        while debuginfod-find debuginfo /run/current-system/sw/bin/make |& grep 'File too large'; do
           sleep 1;
         done
       '')
@@ -56,27 +57,27 @@ in
 
     # nixseparatedebuginfod needs .drv to associate executable -> source
     # on regular systems this would be provided by nixos-rebuild
-    machine.succeed("nix-instantiate '<nixpkgs>' -A nix")
+    machine.succeed("nix-instantiate '<nixpkgs>' -A gnumake")
 
     machine.succeed("timeout 600 wait_for_indexation")
 
     # test debuginfod-find
-    machine.succeed("debuginfod-find debuginfo /run/current-system/sw/bin/nix")
+    machine.succeed("debuginfod-find debuginfo /run/current-system/sw/bin/make")
 
     # test that gdb can fetch source
-    out = machine.succeed("gdb /run/current-system/sw/bin/nix --batch -x ${builtins.toFile "commands" ''
+    out = machine.succeed("gdb /run/current-system/sw/bin/make --batch -x ${builtins.toFile "commands" ''
       start
       l
     ''}")
     print(out)
-    assert 'int main(' in out
+    assert 'main (int argc, char **argv, char **envp)' in out
 
     # test that valgrind can display location information
-    # this relies on the fact that valgrind complains about nix
-    # libgc helps in this regard, and we also ask valgrind to show leak kinds
+    # this relies on the fact that valgrind complains about gnumake
+    # because we also ask valgrind to show leak kinds
     # which are usually false positives.
-    out = machine.succeed("valgrind --leak-check=full --show-leak-kinds=all nix-env --version 2>&1")
+    out = machine.succeed("valgrind --leak-check=full --show-leak-kinds=all make --version 2>&1")
     print(out)
-    assert 'main.cc' in out
+    assert 'main.c' in out
   '';
 }