ci: add Cygwin build workflow

Author: ritesh006

.github/workflows/cygwin-build.yml

@@ -0,0 +1,71 @@
+name: Cygwin build
+
+on:
+  pull_request:
+  push:
+    branches: [ master ]
+
+jobs:
+  cygwin-build:
+    runs-on: windows-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Cygwin with build deps
+        uses: egor-tensin/setup-cygwin@v4
+        with:
+          # Build toolchain + pkg-config + autoconf-archive (for AX_PTHREAD)
+          # Required libs from Profanity docs: libstrophe, ncursesw, glib2, curl, readline, sqlite3
+          packages: >-
+            autoconf
+            automake
+            libtool
+            make
+            pkg-config
+            autoconf-archive
+            gcc-core
+            gettext-devel
+            libstrophe-devel
+            libncursesw-devel
+            libglib2.0-devel
+            libcurl-devel
+            libreadline-devel
+            libsqlite3-devel
+
+      - name: Show versions
+        shell: bash
+        run: |
+          uname -a
+          bash --version
+          gcc --version
+          pkg-config --version
+
+      - name: Autotools bootstrap
+        shell: bash
+        run: |
+          # If the repo uses bootstrap.sh, call it; otherwise do autoreconf
+          if [ -x ./bootstrap.sh ]; then
+            ./bootstrap.sh
+          else
+            autoreconf -fi
+          fi
+
+      - name: Configure
+        shell: bash
+        env:
+          # Avoid CRLF surprises in generated files
+          CYGWIN: winsymlinks:nativestrict
+        run: |
+          ./configure
+
+      - name: Build
+        shell: bash
+        run: |
+          make -j2
+
+      - name: Run basic target checks
+        shell: bash
+        run: |
+          make -n install   # dry-run install just to validate rules