Fix: use posix sh in workflow

Author: han-jiang277

.github/workflows/reusable_cross_repos_build.yml

@@ -63,7 +63,6 @@ jobs:
               });
               fetched_prs.push({owner: owner, repo: repo, pr_num: pr_num, sha: pullRequest.head.sha});
             }));
-
             // Download diffs.
             await Promise.all(patchUrls.map(async ({ repo, url }) => {
               console.log(`Downloading ${url}`);
@@ -87,13 +86,13 @@ jobs:
           for patch in patches/*.diff; do
             patch_abspath=$(realpath ${patch})
             repo=$(basename ${patch} ".diff")
-            if [[ ${repo} != "manifests" ]];then
+            if [ "${repo}" != "manifests" ]; then
               cd ${repo}
             else
               cd .repo/${repo}
             fi
             git apply -3 --check --verbose ${patch_abspath} && git apply -3 --verbose ${patch_abspath}
-            if [[ $? != 0 ]]; then
+            if [ $? != 0 ]; then
               exit 1
             fi
             cd - > /dev/null