Add a CI build to check postgres repository changes. (#702)

The CI builds Postgres from the source code in this branch installed in the
neon vendor/postgres-vXX directory, and then runs the Postgres regression
tests and a very simple Neon test that just does CREATE EXTENSION neon.

This allows making sure we can still build Neon with the current code in the
branch, and load the neon shared library at the server's start-up. Actual
neon testing is still maintained in the neon repository, the goal of this CI
action is to have a minimum amount of feedback when contributing to the
Postgres repository.

Author: dimitri

.github/workflows/build.yml

@@ -0,0 +1,59 @@
+name: Build Postgres
+
+on:
+  push:
+    branches:
+    - REL_16_STABLE_neon
+  pull_request:
+    branches:
+    - REL_16_STABLE_neon
+
+jobs:
+  build_postgres:
+    name: Build Postgres
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Postgres Build Dependencies
+        run: |
+          sudo apt-get install build-essential coreutils libreadline-dev zlib1g-dev flex bison libxml2-dev libxslt-dev libssl-dev libxml2-utils xsltproc git
+
+      - name: Install Neon Build Dependencies
+        run: |
+          sudo apt install libtool libseccomp-dev clang pkg-config cmake postgresql-client protobuf-compiler libprotobuf-dev libcurl4-openssl-dev openssl libicu-dev
+
+      - name: Checkout Neon main branch
+        run: |
+          git clone https://github.com/neondatabase/neon ./neon
+
+      - name: Checkout postgres repository
+        uses: actions/checkout@v4
+        with:
+          path: './neon/vendor/postgres-v16'
+
+      - name: Build PostgreSQL and Neon Extension
+        run: |
+          make -s -j`nproc` -C ./neon -s neon-pg-ext-v16
+
+      - name: Run PostgreSQL Test Suite
+        run: |
+          make -s -j`nproc` -C ./neon/build/v16 check
+
+      - name: Append Postgres binaries to the PATH
+        run: |
+          echo "./neon/pg_install/v16/bin" >> "$GITHUB_PATH"
+
+      - name: Start Postgres
+        run: |
+          pg_ctl init  --pgdata ./data
+          pg_ctl start --pgdata ./data -o '-c shared_preload_libraries=neon'
+
+      - name: Create Extension Neon
+        env:
+          PGHOST: /tmp
+          PGDATABASE: postgres
+        run: |
+          psql --echo-queries --command 'create extension neon;'
+
+      - name: Stop Postgres
+        run: |
+          pg_ctl stop --pgdata ./data