Bump buildx to master to check if it builds on the CI

Signed-off-by: Silvin Lubecki <silvin.lubecki@docker.com>
(cherry picked from commit 0dddbfc)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Upstream-commit: ab2a2b1fae0f643752faf57d22142397147fd83b
Component: packaging

Author: silvin-lubecki

components/packaging/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=v0.3.1}"
+: "${BUILDX_COMMIT=master}"
 DEST=${GOPATH}/src/${PKG}
 
 build() {