Merge pull request #650 from crazy-max/buildx_0.8.1

update buildx to v0.8.1

Author: thaJeztah

plugins/buildx.installer

@@ -6,7 +6,7 @@ source "$(dirname "$0")/.common"
 PKG=github.com/docker/buildx
 GOPATH=$(go env GOPATH)
 REPO=https://${PKG}.git
-: "${BUILDX_COMMIT=v0.8.0}"
+: "${BUILDX_COMMIT=v0.8.1}"
 DEST=${GOPATH}/src/${PKG}
 
 build() {