lts-check-last-commit.sh: fix bug

It didn't consider the first build, fix it

Change-Id: I23e0c49af7c38a76128e50e413c045420a4ee366
Signed-off-by: Arthur She <arthur.she@linaro.org>
diff --git a/scripts/lts-check-last-commit.sh b/scripts/lts-check-last-commit.sh
index 574c306..cda4e34 100755
--- a/scripts/lts-check-last-commit.sh
+++ b/scripts/lts-check-last-commit.sh
@@ -2,31 +2,34 @@
 #
 set -ex
 
-last_build=$((${BUILD_NUMBER}-1))
+TO_BUILD_FILE="${WORKSPACE}/TO_BUILD"
 JOB_URL=${JOB_URL//http:/https:}
 API_URL="${JOB_URL}/${last_build}/api/json"
-
-TO_BUILD_FILE="${WORKSPACE}/TO_BUILD"
-repos_to_check="trusted-firmware-a tf-a-tests tf-a-ci-scripts"
-last_build=$(curl -s ${API_URL})
-last_build_ts=$(echo ${last_build} | jq '.timestamp')
-last_build_ts=$((${last_build_ts}/1000))
-last_build_result=$(echo ${last_build} | jq -r '.result')
-
-if [ "${FORCE_TO_BUILD}" = "true" -o "${last_build_result}" = "FAILURE" ]; then
+last_build=$((${BUILD_NUMBER}-1))
+if [ ${last_build} -eq 0 ]; then
+    echo "This is the first build"
     touch ${TO_BUILD_FILE}
 else
-    for r in ${repos_to_check}
-    do
-        pushd ${SHARE_FOLDER}/${r}
-        last_commit_ts=$(git show --no-patch --format=%ct)
-        # if the last commit was not covered by the last build
-        # the new build will be proceeded
-        if [ ${last_commit_ts} -ge ${last_build_ts} ]; then
-            touch ${TO_BUILD_FILE}
-            break
-        fi
-        popd
-    done
-fi
+    repos_to_check="trusted-firmware-a tf-a-tests tf-a-ci-scripts"
+    last_build=$(curl -s ${API_URL})
+    last_build_ts=$(echo ${last_build} | jq '.timestamp')
+    last_build_ts=$((${last_build_ts}/1000))
+    last_build_result=$(echo ${last_build} | jq -r '.result')
 
+    if [ "${FORCE_TO_BUILD}" = "true" -o "${last_build_result}" = "FAILURE" ]; then
+        touch ${TO_BUILD_FILE}
+    else
+        for r in ${repos_to_check}
+        do
+            pushd ${SHARE_FOLDER}/${r}
+            last_commit_ts=$(git show --no-patch --format=%ct)
+            # if the last commit was not covered by the last build
+            # the new build will be proceeded
+            if [ ${last_commit_ts} -ge ${last_build_ts} ]; then
+                touch ${TO_BUILD_FILE}
+                break
+            fi
+            popd
+        done
+    fi
+fi