Add docker buildx bake configuration (#31477)

Signed-off-by: Amr Mahdi <amrmahdi@meta.com>

docker/docker-bake.hcl

+# docker-bake.hcl - vLLM Docker build configuration
+#
+# This file lives in vLLM repo at docker/docker-bake.hcl
+#
+# Usage:
+#   cd docker && docker buildx bake        # Build default target (openai)
+#   cd docker && docker buildx bake test   # Build test target
+#   docker buildx bake --print             # Show resolved config
+#
+# Reference: https://docs.docker.com/build/bake/reference/
+
+# Build configuration
+
+variable "MAX_JOBS" {
+  default = 16
+}
+
+variable "NVCC_THREADS" {
+  default = 8
+}
+
+variable "TORCH_CUDA_ARCH_LIST" {
+  default = "8.0 8.9 9.0 10.0"
+}
+
+variable "COMMIT" {
+  default = ""
+}
+
+# Groups
+
+group "default" {
+  targets = ["openai"]
+}
+
+# Base targets
+
+target "_common" {
+  dockerfile = "docker/Dockerfile"
+  context    = "."
+  args = {
+    max_jobs             = MAX_JOBS
+    nvcc_threads         = NVCC_THREADS
+    torch_cuda_arch_list = TORCH_CUDA_ARCH_LIST
+  }
+}
+
+target "_labels" {
+  labels = {
+    "org.opencontainers.image.source"      = "https://github.com/vllm-project/vllm"
+    "org.opencontainers.image.vendor"      = "vLLM"
+    "org.opencontainers.image.title"       = "vLLM"
+    "org.opencontainers.image.description" = "vLLM: A high-throughput and memory-efficient inference and serving engine for LLMs"
+    "org.opencontainers.image.licenses"    = "Apache-2.0"
+    "org.opencontainers.image.revision"    = COMMIT
+  }
+  annotations = [
+      "index,manifest:org.opencontainers.image.revision=${COMMIT}",
+  ]
+}
+
+# Build targets
+
+target "test" {
+  inherits = ["_common", "_labels"]
+  target   = "test"
+  tags     = ["vllm:test"]
+  output   = ["type=docker"]
+}
+
+target "openai" {
+  inherits = ["_common", "_labels"]
+  target   = "vllm-openai"
+  tags     = ["vllm:openai"]
+  output   = ["type=docker"]
+}