GHA/non-native: restore MS-DOS jobs

In `!ssl` variant.

It's useful to catch `uint32_t` mismatches with `unsigned int` or its
printf mask.

Also add Renovate version bump rule.

It takes about 1m (autotools) + 30s (cmake) in CI.

Bug: https://github.com/curl/curl/pull/20199#discussion_r2666363334
Follow-up to 8881a52ab0 #20210
Follow-up to e70436a88a #20200
Follow-up to 0630e66cb4 #18338

Closes #20204

.github/workflows/non-native.yml

@@ -329,3 +329,111 @@ jobs:
           else
             make -C bld examples
           fi
+
+  msdos:
+    name: "MS-DOS, ${{ matrix.build == 'cmake' && 'CM' || 'AM' }} djgpp !ssl i586"
+    runs-on: 'ubuntu-latest'
+    timeout-minutes: 5
+    env:
+      MAKEFLAGS: -j 5
+      MATRIX_BUILD: '${{ matrix.build }}'
+      # renovate: datasource=github-releases depName=andrewwutw/build-djgpp versioning=semver-coerced registryUrl=https://github.com
+      TOOLCHAIN_VERSION: '3.4'
+    strategy:
+      matrix:
+        build: [autotools, cmake]
+      fail-fast: false
+    steps:
+      - name: 'install packages'
+        run: |
+          sudo rm -f /var/lib/man-db/auto-update
+          sudo apt-get -o Dpkg::Use-Pty=0 install libfl2
+
+      - name: 'cache compiler (djgpp)'
+        uses: actions/cache@9255dc7a253b0ccc959486e2bca901246202afeb # v5.0.1
+        id: cache-compiler
+        with:
+          path: ~/djgpp
+          key: ${{ runner.os }}-djgpp-${{ env.TOOLCHAIN_VERSION }}-amd64
+
+      - name: 'install compiler (djgpp)'
+        if: ${{ steps.cache-compiler.outputs.cache-hit != 'true' }}
+        run: |
+          cd ~
+          curl --disable --fail --silent --show-error --connect-timeout 15 --max-time 120 --retry 3 --retry-connrefused \
+            --location "https://github.com/andrewwutw/build-djgpp/releases/download/v${TOOLCHAIN_VERSION}/djgpp-linux64-gcc1220.tar.bz2" | tar -xj
+          cd djgpp
+          for f in wat3211b.zip zlb13b.zip; do
+            curl --disable --fail --silent --show-error --connect-timeout 15 --max-time 60 --retry 3 --retry-connrefused \
+              "https://www.delorie.com/pub/djgpp/current/v2tk/$f" --output bin.zip
+            unzip -q bin.zip
+            rm -f bin.zip
+          done
+
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+        with:
+          persist-credentials: false
+
+      - name: 'configure'
+        run: |
+          if [ "${MATRIX_BUILD}" = 'cmake' ]; then
+            cmake -B bld -G Ninja \
+              -DCMAKE_SYSTEM_NAME=DOS \
+              -DCMAKE_SYSTEM_PROCESSOR=x86 \
+              -DCMAKE_C_COMPILER_TARGET=i586-pc-msdosdjgpp \
+              -DCMAKE_C_COMPILER="$HOME/djgpp/bin/i586-pc-msdosdjgpp-gcc" \
+              -DCMAKE_UNITY_BUILD=ON \
+              -DCURL_WERROR=ON \
+              -DCURL_ENABLE_SSL=OFF -DCURL_USE_LIBPSL=OFF \
+              -DZLIB_INCLUDE_DIR="$HOME/djgpp/include" \
+              -DZLIB_LIBRARY="$HOME/djgpp/lib/libz.a" \
+              -DWATT_ROOT="$HOME/djgpp/net/watt"
+          else
+            autoreconf -fi
+            mkdir bld && cd bld && ../configure --disable-dependency-tracking --enable-unity --enable-warnings --enable-werror --disable-shared \
+              CC="$HOME/djgpp/bin/i586-pc-msdosdjgpp-gcc" \
+              AR="$HOME/djgpp/bin/i586-pc-msdosdjgpp-ar" \
+              RANLIB="$HOME/djgpp/bin/i586-pc-msdosdjgpp-ranlib" \
+              WATT_ROOT="$HOME/djgpp/net/watt" \
+              --host=i586-pc-msdosdjgpp \
+              --without-ssl --without-libpsl \
+              --with-zlib="$HOME/djgpp"
+          fi
+
+      - name: 'configure log'
+        if: ${{ !cancelled() }}
+        run: cat bld/config.log bld/CMakeFiles/CMake*.yaml 2>/dev/null || true
+
+      - name: 'curl_config.h'
+        run: |
+          echo '::group::raw'; cat bld/lib/curl_config.h || true; echo '::endgroup::'
+          grep -F '#define' bld/lib/curl_config.h | sort || true
+
+      - name: 'build'
+        run: |
+          if [ "${MATRIX_BUILD}" = 'cmake' ]; then
+            cmake --build bld
+          else
+            make -C bld
+          fi
+
+      - name: 'curl info'
+        run: find . \( -name '*.exe' -o -name '*.a' \) -exec file '{}' \;
+
+      - name: 'build tests'
+        if: ${{ matrix.build == 'cmake' }}  # skip for autotools to save time
+        run: |
+          if [ "${MATRIX_BUILD}" = 'cmake' ]; then
+            cmake --build bld --target testdeps
+          else
+            make -C bld -C tests
+          fi
+
+      - name: 'build examples'
+        if: ${{ matrix.build == 'cmake' }}  # skip for autotools to save time
+        run: |
+          if [ "${MATRIX_BUILD}" = 'cmake' ]; then
+            cmake --build bld --target curl-examples-build
+          else
+            make -C bld examples
+          fi