Add ppc64le and s390x architecture

Changes:
- Add ppc64le and s390x to the multi-build pipeline

Author: sayan-biswas

.tekton/source-to-image-pull-request.yaml

@@ -108,6 +108,8 @@ spec:
     - default:
       - linux/x86_64
       - linux/arm64
+      - linux/ppc64le
+      - linux/s390x
       description: List of platforms to build the container images on. The available
         set of values is determined by the configuration of the multi-platform-controller.
       name: build-platforms

.tekton/source-to-image-push.yaml

@@ -105,6 +105,8 @@ spec:
     - default:
       - linux/x86_64
       - linux/arm64
+      - linux/ppc64le
+      - linux/s390x
       description: List of platforms to build the container images on. The available
         set of values is determined by the configuration of the multi-platform-controller.
       name: build-platforms

Dockerfile

@@ -6,7 +6,7 @@ ENV S2I_GIT_VERSION="1.4.0" \
 
 COPY . .
 
-RUN CGO_ENABLED=0 go build -a -ldflags="-s -w" -o /tmp/s2i ./cmd/s2i
+RUN CGO_ENABLED=0 GO111MODULE=on go build -a -mod=vendor -ldflags="-s -w" -o /tmp/s2i ./cmd/s2i
 
 #
 # Runner Image
@@ -25,7 +25,6 @@ LABEL \
     description="Source-to-Image is a builder image" \
     summary="Source-to-Image is a builder image" \
     version="1.4.0" \
-    architecture="${GOARCH}" \
     vendor="Red Hat, Inc." \
     com.redhat.component="source-to-image-container" \
     maintainer="[email protected]" \