try to run CI on github actions

.github/workflows/main.yml

@@ -0,0 +1,17 @@
+name: main
+on: [push, pull_request]
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+    steps:
+      - uses: actions/checkout@v2
+      - name: configure
+        run: cmake -B build -D CMAKE_BUILD_TYPE=Release 
+      - name: build
+        run: cmake --build build --parallel 2
+      # unfortunately the tests manipulate tap/tun drivers. This is not allowed in GA
+      # - name: test
+      #   run: cd build && ctest -VV

regress/CMakeLists.txt

@@ -14,10 +14,9 @@ foreach(SOURCE_FILE ${ALL_C_TESTS})
            COMMAND $<TARGET_FILE:${TEST_NAME}>)
 endforeach(SOURCE_FILE)
 
-# Shell based tests (needs a posix shell and `ip' command)
+# Shell based tests (needs a posix shell)
 # -----------------
-find_program(IP_COMMAND ip)
-if (IP_COMMAND)
+if (UNIX)
   file(GLOB ALL_SH_TESTS test*.sh)
   foreach(SOURCE_FILE ${ALL_SH_TESTS})
     get_filename_component(TEST_NAME ${SOURCE_FILE} NAME_WE)