plugins: update buildx to v0.4.2

full diff: docker/buildx@v0.4.1...v0.4.2

- bake: fix parsing json config with hcl v2
- bake: update go-cty to pull in more stdlib funcs
- bake: ensure --builder is wired from root options
- build: support cacheonly exporter
- build: improve error checking on load
- build: remove warning for multi-platform iidfile

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit a6de61c)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Upstream-commit: 55f0b0c52db3821ed11c16604a1ba3e3cfa4b63e
Component: packaging

Author: thaJeztah

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=v0.4.1}"
+: "${BUILDX_COMMIT=v0.4.2}"
 DEST=${GOPATH}/src/${PKG}
 
 build() {