ci(packages): fix the path filter reporting "not changed" on SIGPIPE

`printf | grep -q` under pipefail fails when grep exits on the first match
and printf takes SIGPIPE, so the first run marked every package unchanged and
the gate passed with nothing tested. Match with a here-string instead, and
print a count rather than every changed path.

Signed-off-by: Richard Abrich <richard.abrich@mldsai.com>

Author: abrichr

.github/workflows/packages.yml

@@ -66,8 +66,10 @@ jobs:
               ;;
           esac
           changed="$(git diff --name-only "$base" HEAD)"
-          printf '%s\n' "$changed" | sed 's/^/changed: /'
-          hit() { if printf '%s\n' "$changed" | grep -Eq "$1"; then echo true; else echo false; fi; }
+          echo "$(grep -c . <<<"$changed" || true) changed paths"
+          # A here-string, not a pipe: with pipefail, `printf | grep -q` can
+          # fail on SIGPIPE and silently report "not changed".
+          hit() { if grep -Eq "$1" <<<"$changed"; then echo true; else echo false; fi; }
           wf='^\.github/workflows/packages\.yml$'
           flow="$(hit "^packages/flow/|$wf")"
           types="$(hit "^packages/types/|$wf")"