Add macos-only build file so can test mac builds quickly

.github/workflows/macos.yml

@@ -0,0 +1,38 @@
+name: Build for all platforms
+
+on:
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  macOS:
+    runs-on: macos-11.0
+
+    steps:
+    - name: Install Rust
+      uses: actions-rs/toolchain@v1
+      with:
+          toolchain: stable
+
+    - name: Checkout
+      uses: actions/checkout@v2
+
+    - name: Install deps
+      run: |
+          brew install ffmpeg@5
+          brew link ffmpeg@5
+
+    - name: Build
+      run: |
+        mkdir releases
+        cargo build --release
+        strip target/release/bliss-analyser
+        cp target/release/bliss-analyser releases/bliss-analyser
+
+    - name: Upload artifacts
+      uses: actions/upload-artifact@v2
+      with:
+        name: bliss-analyser-mac
+        path: releases/