use git sha for postgres build cache

.github/workflows/build_and_test.yaml

@@ -48,12 +48,13 @@ jobs:
         run: ruff check --output-format=github .
       - name: Run ruff format
         run: ruff format --diff
+
   build-and-test:
     name: 'Build and test'
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest]
+        os: [ubuntu-24.04]
         version: [REL_16_STABLE, REL_17_STABLE]
     runs-on: ${{ matrix.os }}
 
@@ -81,26 +82,33 @@ jobs:
           submodules: 'recursive'
           path: duckdb
 
-      - name: Compute DuckDB SHA
+      - name: Checkout PostgreSQL code
+          rm -rf postgres
+          git clone --branch ${{ matrix.version }} --single-branch --depth 1 https://github.com/postgres/postgres.git
+
+      - name: Compute Version SHAs
         id: versions
         run: |
           pushd duckdb
           DUCKDB_SHA=`git ls-tree HEAD third_party/duckdb --format='%(objectname)'`
           echo "duckdb_sha=${DUCKDB_SHA}" >> "$GITHUB_OUTPUT"
           echo "Got DUCKDB_SHA='${DUCKDB_SHA}'"
+          popd
+          pushd postgres
+          POSTGRES_SHA=`git ls-tree HEAD --format='%(objectname)'`
+          echo "postgres_sha=${POSTGRES_SHA}" >> "$GITHUB_OUTPUT"
+          echo "Got POSTGRES_SHA='${POSTGRES_SHA}'"
 
       - name: Setup PG build cache
         id: cache-pg-build
         uses: actions/cache@v4
         with:
           path: postgres/inst
-          key: pg-build-${{ matrix.version }}
+          key: pg-build-${{ steps.versions.outputs.postgres_sha }}
 
-      - name: Checkout and build PostgreSQL code
+      - name: Build PostgreSQL code
         if: steps.cache-pg-build.outputs.cache-hit != 'true'
         run: |
-          rm -rf postgres
-          git clone --branch ${{ matrix.version }} --single-branch --depth 1 https://github.com/postgres/postgres.git
           pushd postgres
           git branch
           ./configure --prefix=$PWD/inst/ --enable-cassert --enable-debug --with-openssl --with-icu --with-libxml