Test if plugins are compiling for new commit and pull requests

Doesn't include VST2 due to lack of headers in repo.

MSVC build is disabled due to internal compiler error.
No MinGW build for Windows due to its complexity.

.github/workflows/githubci.yml

@@ -0,0 +1,45 @@
+name: CMake Build Matrix
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    name: ${{ matrix.config.name }}
+    runs-on: ${{ matrix.config.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        config:
+#          MSVC compiler 16.5.0+d4cbfca49 crashes with:
+#            ladspa++.h(655,1): fatal error C1001: Internal compiler error.
+#
+#          - {
+#            name: "Windows Latest MSVC",
+#            os: windows-latest,
+#            cc: "cl", cxx: "cl",
+#            environment_script: "C:/Program Files (x86)/Microsoft Visual Studio/2019/Enterprise/VC/Auxiliary/Build/vcvars64.bat"
+#          }
+          - {
+            name: "Ubuntu Latest GCC",
+            os: ubuntu-latest,
+            cc: "gcc", cxx: "g++"
+          }
+          - {
+            name: "macOS Latest Clang",
+            os: macos-latest,
+            cc: "clang", cxx: "clang++"
+          }
+
+    steps:
+      - uses: actions/checkout@v1
+
+      - name: Configure
+        env:
+          CC: ${{ matrix.config.cc }}
+          CXX: ${{ matrix.config.cxx }}
+        run: |
+          cmake -Bbuild -DCMAKE_BUILD_TYPE=Release
+
+      - name: Build
+        run: |
+          cmake --build build