Merge pull request moby#4017 from crazy-max/test-set-goversion

hack: allow to set GO_VERSION during tests

Author: crazy-max

hack/test

@@ -3,6 +3,7 @@
 . $(dirname $0)/util
 set -eu -o pipefail
 
+: ${GO_VERSION=}
 : ${HTTP_PROXY=}
 : ${HTTPS_PROXY=}
 : ${NO_PROXY=}
@@ -74,6 +75,7 @@ if [[ "$GOBUILDFLAGS" == *"-race"* ]]; then
 fi
 
 buildxCmd build $cacheFromFlags \
+  --build-arg GO_VERSION \
   --build-arg BUILDKITD_TAGS \
   --build-arg HTTP_PROXY \
   --build-arg HTTPS_PROXY \