Fix ghcr-upload.sh: null byte crash from binary NAR in store-paths.txt

The old code piped `nix-store --export` (binary NAR output containing
null bytes) through `tee store-paths.txt`, then used `tail -n 1` on
that binary file inside $() — bash on Ubuntu 24.04 errors out with
"command substitution: ignored null byte in input".

Fix: capture the text path list from `nix-store -qR` in a variable
first, then use grep to verify the -env.sh script is in the closure.

Author: angerman

extra/ghcr-upload.sh

@@ -7,9 +7,13 @@ set -euox pipefail
 
 # retry three times in case of intermittent network errors.
 nix-store -r "$SHELL_NIX_PATH" || nix-store -r "$SHELL_NIX_PATH" || nix-store -r "$SHELL_NIX_PATH"
-#nix build ".#hydraJobs.${DEV_SHELL}" --show-trace --accept-flake-config
-nix-store --export $(nix-store -qR "$SHELL_NIX_PATH") | tee store-paths.txt | zstd -z8T8 >${DEV_SHELL}
-# Verify the environment script is included in the closure
-# The script filename ends with -env.sh (e.g., ghc96-env.sh, ghc98-static-iog-env.sh)
-if [[ ! $(tail -n 1 store-paths.txt) =~ "-env.sh" ]]; then exit 1; fi
+# Collect closure paths and export them as a zstd-compressed NAR archive.
+# Save the path list separately for verification — nix-store --export
+# produces binary output (contains null bytes) which can't be inspected
+# with text tools like tail/grep.
+CLOSURE_PATHS=$(nix-store -qR "$SHELL_NIX_PATH")
+nix-store --export $CLOSURE_PATHS | zstd -z8T8 >${DEV_SHELL}
+# Verify the environment script is included in the closure.
+# The script filename ends with -env.sh (e.g., ghc96-env.sh, ghc98-static-iog-env.sh).
+if ! echo "$CLOSURE_PATHS" | grep -q -- "-env\.sh$"; then exit 1; fi
 oras push ghcr.io/input-output-hk/devx:${DEV_SHELL} ${DEV_SHELL}