Add CI for checking file size (#14274)

As title. xrefs will hang if the files change too much, however it's a
bit hard to tell. Make file size check explicit. The rule is following
1. For all files, the file size can't be larger than 1MB
2. For images/vidoes, the files size can't be larger than 7MB
3. There is an exception list defined in the script if it's really
needed

Author: cccclai

.github/workflows/_link_check.yml

@@ -55,3 +55,29 @@ jobs:
           echo "Or add \`@lint-ignore\` somewhere on the same line as the reference you want to skip checking."
           exit 1
         }
+
+  lint-file-size:
+    if: ${{ github.event_name == 'pull_request' }}
+    uses: pytorch/test-infra/.github/workflows/linux_job_v2.yml@main
+    with:
+      runner: linux.2xlarge
+      docker-image: ci-image:executorch-ubuntu-22.04-linter
+      submodules: false
+      fetch-depth: 0
+      ref: ${{ inputs.ref }}
+      timeout: 30
+      script: |
+        chmod +x ./scripts/lint_file_size.sh
+        ./scripts/lint_file_size.sh $(
+          if [ "${{ github.event_name }}" = "pull_request" ]; then
+            echo "${{ github.event.pull_request.base.sha }}" "${{ github.event.pull_request.head.sha }}"
+          else
+            echo "${{ github.event.before }}" "${{ github.sha }}"
+          fi
+        ) || {
+          echo
+          echo "File size lint failed: some files exceed the 1 MB limit."
+          echo "If you really need large files, consider using Git LFS or storing them elsewhere."
+          echo "If you really need to get unblocked and check in the file, can add it to the EXCEPTIONS list in scripts/lint_file_size.sh."
+          exit 1
+        }

scripts/lint_file_size.sh

@@ -0,0 +1,73 @@
+#!/bin/bash
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+set -euo pipefail
+
+status=0
+
+green='\e[1;32m'; red='\e[1;31m'; cyan='\e[1;36m'; reset='\e[0m'
+
+# Following is the rules for the file size linting:
+# 1. For all files, the file size can't be larger than 1MB
+# 2. For images/videos, the file size can't be larger than 8MB
+# 3. There is an exception list defined in the script if it's really needed
+
+# List of files to skip (relative paths)
+EXCEPTIONS=(
+  "examples/models/llama/params/demo_rand_params.pth"
+  "examples/models/llama/tokenizer/test/resources/test_tiktoken_tokenizer.model"
+  "examples/qualcomm/oss_scripts/llama/artifacts/stories260k_hybrid_llama_qnn.pte"
+  # Following needs to be clean up
+  "examples/mediatek/models/llm_models/weights/Llama-3.2-1B-Instruct/tokenizer.json"
+  "examples/mediatek/models/llm_models/weights/Llama-3.2-3B-Instruct/tokenizer.json"
+  "examples/mediatek/models/llm_models/weights/llama3-8B-instruct/tokenizer.json"
+)
+
+is_exception() {
+  local f=$1
+  for ex in "${EXCEPTIONS[@]}"; do
+    if [[ "$f" == "$ex" ]]; then
+      return 0
+    fi
+  done
+  return 1
+}
+
+if [ $# -eq 2 ]; then
+  base=$1
+  head=$2
+  echo "Checking changed files between $base...$head"
+  files=$(git diff --name-only "$base...$head")
+else
+  echo "Checking all files in repository"
+  files=$(git ls-files)
+fi
+
+for file in $files; do
+  if is_exception "$file"; then
+    echo -e "${cyan}SKIP${reset}  $file (in exception list)"
+    continue
+  fi
+  if [ -f "$file" ]; then
+    # Set size limit depending on extension
+    if [[ "$file" =~ \.(png|jpg|jpeg|gif|svg|mp3|mp4)$ ]]; then
+      MAX_SIZE=$((8 * 1024 * 1024))  # 8 MB for pictures
+    else
+      MAX_SIZE=$((1 * 1024 * 1024))  # 1 MB for others
+    fi
+
+    size=$(wc -c <"$file")
+    if [ "$size" -gt "$MAX_SIZE" ]; then
+      echo -e "${red}FAIL${reset} $file (${cyan}${size} bytes${reset}) exceeds ${MAX_SIZE} bytes"
+      status=1
+    else
+      echo -e "${green}OK${reset}   $file (${size} bytes)"
+    fi
+  fi
+done
+
+exit $status