Merge bitcoin/bitcoin#21749: test: Bump shellcheck version

08f3dbb1b0 test: Bump shellcheck version (Hennadii Stepanov)

Pull request description:

  The changelog for v0.7.2 is available [here](https://github.com/koalaman/shellcheck/blob/v0.7.2/CHANGELOG.md).

  Only [SC2268](https://github.com/koalaman/shellcheck/wiki/SC2268) requires to update our code.

ACKs for top commit:
  jarolrod:
    ACK  08f3dbb1b0

Tree-SHA512: 4585cd1f4d9def2fbaafe5a2a57761288d432781eb8c6c6d37064727d7ca8fc3f35c552e6a2ffdf0820d753d4bde2c8e43e5f3f57d242f5f57591a9b1b03558d

test/lint/commit-script-check.sh

@@ -12,7 +12,7 @@
 # one. Any remaining diff signals an error.
 
 export LC_ALL=C
-if test "x$1" = "x"; then
+if test -z $1; then
     echo "Usage: $0 <commit>..."
     exit 1
 fi
@@ -24,7 +24,7 @@ for commit in $(git rev-list --reverse $1); do
     if git rev-list -n 1 --pretty="%s" $commit | grep -q "^scripted-diff:"; then
         git checkout --quiet $commit^ || exit
         SCRIPT="$(git rev-list --format=%b -n1 $commit | sed '/^-BEGIN VERIFY SCRIPT-$/,/^-END VERIFY SCRIPT-$/{//!b};d')"
-        if test "x$SCRIPT" = "x"; then
+        if test -z "$SCRIPT"; then
             echo "Error: missing script for: $commit"
             echo "Failed"
             RET=1