ci: add yamllint

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

.github/labeler.yml

@@ -1,4 +1,3 @@
-
 # Add 'area/project' label to changes in basic project documentation and .github folder, excluding .github/workflows
 area/project:
   - all:

docker-bake.hcl

@@ -31,7 +31,7 @@ group "default" {
 }
 
 group "validate" {
-  targets = ["lint", "lint-gopls", "validate-golangci", "validate-vendor", "validate-docs"]
+  targets = ["lint", "lint-gopls", "lint-yaml", "validate-golangci", "validate-vendor", "validate-docs"]
 }
 
 target "lint" {
@@ -64,6 +64,14 @@ target "lint-gopls" {
   target = "gopls-analyze"
 }
 
+target "lint-yaml" {
+  description = "Lint Github Actions workflows and other YAML files"
+  inherits = ["_common"]
+  dockerfile = "./hack/dockerfiles/lint.Dockerfile"
+  target = "yamllint"
+  output = ["type=cacheonly"]
+}
+
 target "validate-vendor" {
   inherits = ["_common"]
   dockerfile = "./hack/dockerfiles/vendor.Dockerfile"

hack/dockerfiles/lint.Dockerfile

@@ -75,4 +75,10 @@ RUN --mount=target=. \
   done
 EOF
 
+FROM alpine AS yamllint
+RUN apk add --no-cache yamllint
+WORKDIR /go/src/github.com/docker/buildx
+RUN --mount=type=bind \
+  yamllint -c .yamllint.yml --strict .
+
 FROM lint