Added s390x support for docker image (#1539)

Signed-off-by: Vitthal Bagal <vitthalb@us.ibm.com>

.circleci/config.yml

@@ -40,7 +40,7 @@ jobs:
 
     steps:
     - checkout
-    - run: docker run --privileged linuxkit/binfmt:v0.6
+    - run: docker run --privileged linuxkit/binfmt:v0.7
     - run: make promu
     - run: promu crossbuild
     - run: promu --config .promu-cgo.yml crossbuild

.dockerignore

@@ -5,3 +5,4 @@
 !.build/linux-armv7
 !.build/linux-arm64
 !.build/linux-ppc64le
+!.build/linux-s390x

Makefile

@@ -15,7 +15,7 @@
 all::
 
 # Needs to be defined before including Makefile.common to auto-generate targets
-DOCKER_ARCHS ?= amd64 armv7 arm64 ppc64le
+DOCKER_ARCHS ?= amd64 armv7 arm64 ppc64le s390x
 
 include Makefile.common