Fix bad build result comparison.

Also apply https://google.github.io/styleguide/shell.xml and
https://sipb.mit.edu/doc/safe-shell/ while I'm in here.

hack/jenkins/minikube_cross_build_and_upload.sh

@@ -21,31 +21,35 @@
 # ghprbPullId: The pull request ID, injected from the ghpbr plugin.
 # ghprbActualCommit: The commit hash, injected from the ghpbr plugin.
 
-set -e
+set -eux -o pipefail
 
-export BUILD_IN_DOCKER=y
-export TAG=$ghprbActualCommit
-export GOPATH=/var/lib/jenkins/go
+declare -rx BUILD_IN_DOCKER=y
+declare -rx GOPATH=/var/lib/jenkins/go
+declare -rx ISO_BUCKET="minikube-builds/${ghprbPullId}"
+declare -rx ISO_VERSION="testing"
+declare -rx TAG="${ghprbActualCommit}"
+
+readonly bucket="gs://minikube-builds"
 
 docker kill $(docker ps -q) || true
 docker rm $(docker ps -aq) || true
-set +e
-make -j 16 all
-set -e
+make -j 16 all && result=$? || result=$?
 
-make_result="$?"
-gsutil cp gs://minikube-builds/logs/index.html gs://minikube-builds/logs/${ghprbPullId}/index.html
+gsutil cp gs://minikube-builds/logs/index.html \
+  "gs://minikube-builds/logs/${ghprbPullId}/index.html"
 
-# Exit if the cross build failed.
-if [ "$make_result"-ne 0 ]; then echo "cross build failed"; exit 1; fi
+if [[ "${result}" -ne 0 ]]; then
+  echo "build failed"
+  exit "${result}"
+fi
 
-# If there are ISO changes, build and upload the ISO
-# then set the default to the newly built ISO for testing
-if out="$(git diff ${ghprbActualCommit} --name-only $(git merge-base origin/master ${ghprbActualCommit}) | grep deploy/iso/minikube)" &> /dev/null; then
+
+git diff ${ghprbActualCommit} --name-only \
+  $(git merge-base origin/master ${ghprbActualCommit}) \
+  | grep -q deploy/iso/minikube && rebuild_iso=1 || rebuild_iso=0
+
+if [[ "${rebuild_iso}" -eq 1 ]]; then
 	echo "ISO changes detected ... rebuilding ISO"
-	export ISO_BUCKET="minikube-builds/${ghprbPullId}"
-	export ISO_VERSION="testing"
-
 	make release-iso
 fi
 
@@ -54,5 +58,4 @@ cp -r test/integration/testdata out/
 # Don't upload the buildroot artifacts if they exist
 rm -r out/buildroot || true
 
-# Upload everything we built to Cloud Storage.
 gsutil -m cp -r out/* gs://minikube-builds/${ghprbPullId}/