Address review: argc guard in check-dir.sh, fix sbt ubuntu matrix conditionals

- check-dir.sh: with set -u, invoking without a <dir> argument failed with an
  opaque "parameter not set" error. Add an explicit argc check that prints a
  usage message and exits 2 (distinct from the assertion failure code 1).
- e2e-cache.yml: the sbt-save and sbt-restore jobs run on an ubuntu-22.04
  matrix entry, but their coursier-cache steps were guarded by
  'if: matrix.os == "ubuntu-latest"', so those checks never executed on
  Ubuntu. Align the conditionals with the matrix (ubuntu-22.04), matching the
  newer sbt1/sbt2 jobs.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

.github/workflows/e2e-cache.yml

@@ -144,7 +144,7 @@ jobs:
         if: matrix.os == 'windows-latest'
         run: bash "$GITHUB_WORKSPACE/__tests__/check-dir.sh" "$HOME/AppData/Local/Coursier/Cache"
       - name: Check files to cache on ubuntu-latest
-        if: matrix.os == 'ubuntu-latest'
+        if: matrix.os == 'ubuntu-22.04'
         run: bash "$GITHUB_WORKSPACE/__tests__/check-dir.sh" "$HOME/.cache/coursier"
   sbt-restore:
     runs-on: ${{ matrix.os }}
@@ -177,7 +177,7 @@ jobs:
         if: matrix.os == 'windows-latest'
         run: bash "$GITHUB_WORKSPACE/__tests__/check-dir.sh" "$HOME/AppData/Local/Coursier/Cache"
       - name: Confirm that ~/.cache/coursier directory has been made
-        if: matrix.os == 'ubuntu-latest'
+        if: matrix.os == 'ubuntu-22.04'
         run: bash "$GITHUB_WORKSPACE/__tests__/check-dir.sh" "$HOME/.cache/coursier"
   gradle1-save:
     runs-on: ${{ matrix.os }}

__tests__/check-dir.sh

@@ -10,6 +10,11 @@
 # tilde-expansion pitfalls.
 set -eu
 
+if [ "$#" -lt 1 ]; then
+  echo "Usage: check-dir.sh <dir> [present|absent]" >&2
+  exit 2
+fi
+
 dir=$1
 mode=${2:-present}