[host] Speed up builds with ccache when available (#17728)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

.github/workflows/ci.yml

@@ -365,6 +365,12 @@ jobs:
     steps:
       - name: Check out code from GitHub
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Install ccache
+        # Speeds up the host compiles: tests in a bucket compile overlapping
+        # component sets, so later tests reuse earlier tests' objects.
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y --no-install-recommends ccache
       - name: Set up Python 3.13
         id: python
         uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97 # v7.0.0
@@ -409,6 +415,10 @@ jobs:
           mapfile -t test_files < <(echo "$BUCKET_TESTS" | jq -r '.[]')
           echo "Bucket ${{ matrix.bucket.name }}: running ${#test_files[@]} integration tests"
           pytest -vv --no-cov --tb=native --durations=30 -n auto "${test_files[@]}"
+      - name: Print ccache statistics
+        # esphome stores the PlatformIO ccache under the machine-global cache
+        # dir (see _ccache_env() in esphome/platformio/toolchain.py).
+        run: CCACHE_DIR="$HOME/.cache/esphome/platformio-ccache" ccache -s
 
   cpp-unit-tests:
     name: Run C++ unit tests

esphome/components/host/__init__.py

@@ -10,6 +10,7 @@ from esphome.const import (
     ThreadModel,
 )
 from esphome.core import CORE
+from esphome.platformio.toolchain import copy_ccache_script
 
 from .const import KEY_HOST
 
@@ -49,3 +50,9 @@ async def to_code(config):
     cg.add_platformio_option("platform", "platformio/native")
     cg.add_platformio_option("lib_ldf_mode", "off")
     cg.add_platformio_option("lib_compat_mode", "strict")
+    cg.add_platformio_option("extra_scripts", ["pre:ccache.py"])
+
+
+# Called by writer.py
+def copy_files() -> None:
+    copy_ccache_script()