GitHub: add workflow to provide an openocd snapshot binaries for win32

This change could be used within OpenOCD GitHub forks.

Once workflow actions are enabled in the GitHub project, this workflow
will be run automatically on each push into OpenOCD.

This workflow will provide a neutral build of openocd for win32, then
the package will be available for download in Actions section.
Note: the artifact will be deleted after 90 day (actual GitHub rules)

If the push is a tag, the generated package will be uploaded to release
pane under the corresponding release, and it will resides forever.

The built openocd enables libusb1, hidapi and libftdi adapters,
and could be extended to cover more adapters and Oses

PS: ./contrib/cross-build.sh updated to build libftdi from source like
libusb1 and hidapi.

Change-Id: I290c8aa14a12548e2dcb6a0eee456430ea44ab9f
Signed-off-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
Reviewed-on: http://openocd.zylin.com/5594
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

.github/workflows/snapshot.yml

@@ -0,0 +1,92 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+# Copyright (C) 2020 by Tarek BOUCHKATI <tarek.bouchkati@gmail.com>
+
+on: push
+
+name: OpenOCD Snapshot
+
+jobs:
+  package:
+    runs-on: [ubuntu-18.04]
+    env:
+      DL_DIR: ../downloads
+      BUILD_DIR: ../build
+    steps:
+      - name: Install needed packages
+        run: sudo apt-get install autotools-dev autoconf automake libtool pkg-config cmake texinfo texlive g++-mingw-w64-i686
+      - uses: actions/checkout@v1
+      - run: ./bootstrap
+      - name: Prepare libusb1
+        env:
+          LIBUSB1_VER: 1.0.23
+        run: |
+          mkdir -p $DL_DIR && cd $DL_DIR
+          wget "https://github.com/libusb/libusb/releases/download/v${LIBUSB1_VER}/libusb-${LIBUSB1_VER}.tar.bz2"
+          tar -xjf libusb-${LIBUSB1_VER}.tar.bz2
+          echo "::set-env name=LIBUSB1_SRC::$PWD/libusb-${LIBUSB1_VER}"
+      - name: Prepare hidapi
+        env:
+          HIDAPI_VER: 0.9.0
+        run: |
+          mkdir -p $DL_DIR && cd $DL_DIR
+          wget "https://github.com/libusb/hidapi/archive/hidapi-${HIDAPI_VER}.tar.gz"
+          tar -xzf hidapi-${HIDAPI_VER}.tar.gz
+          cd hidapi-hidapi-${HIDAPI_VER}
+          ./bootstrap
+          echo "::set-env name=HIDAPI_SRC::$PWD"
+      - name: Prepare libftdi
+        env:
+          LIBFTDI_VER: 1.4
+        run: |
+          mkdir -p $DL_DIR && cd $DL_DIR
+          wget "http://www.intra2net.com/en/developer/libftdi/download/libftdi1-${LIBFTDI_VER}.tar.bz2"
+          tar -xjf libftdi1-${LIBFTDI_VER}.tar.bz2
+          echo "::set-env name=LIBFTDI_SRC::$PWD/libftdi1-${LIBFTDI_VER}"
+      - name: Package OpenOCD for windows
+        env:
+          MAKE_JOBS: 2
+          HOST: i686-w64-mingw32
+          LIBUSB1_CONFIG: --enable-shared --enable-static
+          HIDAPI_CONFIG: --enable-shared --disable-static --disable-testgui
+          LIBFTDI_CONFIG: "-DCMAKE_TOOLCHAIN_FILE='${{ env.LIBFTDI_SRC }}/cmake/Toolchain-i686-w64-mingw32.cmake' -DBUILD_TESTS:BOOL=off -DFTDIPP:BOOL=off -DPYTHON_BINDINGS:BOOL=off -DEXAMPLES:BOOL=off -DDOCUMENTATION:BOOL=off -DFTDI_EEPROM:BOOL=off"
+        run: |
+          # set snapshot tag
+          OPENOCD_TAG="`git tag --points-at HEAD`"
+          [ -z $OPENOCD_TAG ] && OPENOCD_TAG="`git rev-parse --short HEAD`"
+          # set env and call cross-build.sh
+          export OPENOCD_TAG=$OPENOCD_TAG
+          export OPENOCD_SRC=$PWD
+          export OPENOCD_CONFIG=""
+          mkdir -p $BUILD_DIR &&  cd $BUILD_DIR
+          bash $OPENOCD_SRC/contrib/cross-build.sh $HOST
+          # add missing dlls
+          cd $HOST-root/usr
+          cp `$HOST-gcc --print-file-name=libwinpthread-1.dll` ./bin/
+          cp `$HOST-gcc --print-file-name=libgcc_s_sjlj-1.dll` ./bin/
+          # prepare the artifact
+          ARTIFACT="openocd-${OPENOCD_TAG}-${HOST}.tar.gz"
+          tar -czf $ARTIFACT *
+          echo "::set-env name=ARTIFACT_NAME::$ARTIFACT"
+          echo "::set-env name=ARTIFACT_PATH::$PWD/$ARTIFACT"
+      - name: Publish OpenOCD packaged for windows
+        uses: actions/upload-artifact@v1
+        with:
+          name: ${{ env.ARTIFACT_NAME }}
+          path: ${{ env.ARTIFACT_PATH }}
+      - name: Get the upload URL for a release
+        id: get_release
+        if: startsWith(github.ref, 'refs/tags/')
+        uses: bruceadams/get-release@v1.2.0
+        env:
+          GITHUB_TOKEN: ${{ github.token }}
+      - name: Release OpenOCD packaged for windows
+        if: startsWith(github.ref, 'refs/tags/')
+        uses: actions/upload-release-asset@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          upload_url: ${{ steps.get_release.outputs.upload_url }}
+          asset_path: ${{ env.ARTIFACT_PATH }}
+          asset_name: ${{ env.ARTIFACT_NAME }}
+          asset_content_type: application/gzip