modules/shared: move free-space to bash script

modules/darwin/builder.nix

@@ -15,7 +15,7 @@
       config.nix.package
       pkgs.coreutils
     ];
-    script = import "${inputs.self}/modules/shared/free-space.nix";
+    script = builtins.readFile "${inputs.self}/modules/shared/free-space.bash";
   };
 
   # https://github.com/LnL7/nix-darwin/blob/230a197063de9287128e2c68a7a4b0cd7d0b50a7/modules/nix/default.nix#L201

modules/nixos/builder.nix

@@ -14,7 +14,7 @@
       config.nix.package
       pkgs.coreutils
     ];
-    script = import "${inputs.self}/modules/shared/free-space.nix";
+    script = builtins.readFile "${inputs.self}/modules/shared/free-space.bash";
   };
 
   # Bump the open files limit so that non-root users can run NixOS VM tests

modules/shared/free-space.bash

@@ -0,0 +1,10 @@
+# https://git.lix.systems/the-distro/infra/commit/15a684c5d7e1ee25cdd6f2941ed17c01aa107781
+nix-env --delete-generations 1d --profile /nix/var/nix/profiles/system
+while :; do
+  used=$(($(stat -f --format="100-(100*%a/%b)" /)))
+  if [[ $used -gt "85" ]]; then
+    nix-store --gc --max-freed 100G
+  else
+    break
+  fi
+done

modules/shared/free-space.nix

@@ -1,12 +0,0 @@
-# https://git.lix.systems/the-distro/infra/commit/15a684c5d7e1ee25cdd6f2941ed17c01aa107781
-''
-  nix-env --delete-generations 1d --profile /nix/var/nix/profiles/system
-  while : ; do
-    used=$(($(stat -f --format="100-(100*%a/%b)" /)))
-    if [[ $used -gt "85" ]]; then
-      nix-store --gc --max-freed 100G
-    else
-      break
-    fi
-  done
-''