Fix: build correct func-util binary for give arch (knative#2843)

Signed-off-by: Matej Vašek <[email protected]>

Author: matejvasek

.github/workflows/ci.yaml

@@ -242,7 +242,7 @@ jobs:
       - name: Build and push
         run: |
           for a in amd64 arm64 ppc64le s390x; do
-            CGO_ENABLED=0 go build -o "func-util-$a" -trimpath -ldflags '-w -s' ./cmd/func-util
+            CGO_ENABLED=0 GOARCH="$a" go build -o "func-util-$a" -trimpath -ldflags '-w -s' ./cmd/func-util
           done
           docker buildx create --name multiarch --driver docker-container --use
           docker buildx build . -f Dockerfile.utils \