build-system: add GitHub action for openSUSE Leap 15.2

This way we test a Qt 5.15 build.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

.github/workflows/linux-leap-qt-5.15.yml

@@ -0,0 +1,50 @@
+name: openSUSE 15.2 / Qt 5.15
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
+
+jobs:
+  buildInContainer:
+    runs-on: ubuntu-latest
+    container:
+      image: opensuse/leap:15.2
+
+    steps:
+    - name: checkout sources
+      uses: actions/checkout@v1
+
+    - name: get container ready for build
+      run: |
+        echo "--------------------------------------------------------------"
+        echo "update distro and install dependencies"
+        zypper -n install git gcc-c++ make autoconf automake libtool cmake libzip-devel \
+        libxml2-devel libxslt-devel sqlite3-devel libusb-1_0-devel \
+        libqt5-linguist-devel libqt5-qttools-devel libQt5WebKitWidgets-devel \
+        libqt5-qtbase-devel libQt5WebKit5-devel libqt5-qtsvg-devel \
+        libqt5-qtscript-devel libqt5-qtdeclarative-devel \
+        libqt5-qtconnectivity-devel libqt5-qtlocation-devel libcurl-devel \
+        libQt5QuickControls2-devel bluez-devel \
+        which libgit2-devel libssh2-devel
+
+# if we want to run the tests below, add    xvfb-run
+
+    - name: build Subsurface
+      run: |
+        echo "--------------------------------------------------------------"
+        echo "building desktop"
+
+        # now build for the desktop version (including WebKit)
+        cd ..
+        bash -e -x subsurface/scripts/build.sh -desktop -build-with-webkit
+
+# let's not run the tests... to do that, we need to install 'xvfb-run' above
+#   - name: test desktop build
+#     run: |
+#       echo "--------------------------------------------------------------"
+#       echo "running tests for desktop"
+#       cd build
+#       xvfb-run --auto-servernum make check