ci(obs): ship macOS + Windows binaries only; Linux is build-from-source

The Linux plugin would link the nix/distro ffmpeg rather than the version OBS
bundles, so it isn't portable. macOS and Windows link the obs-deps ffmpeg OBS
ships, so those binaries are portable. Drop the Linux legs from the release
matrix (no second cargo build / nix step needed now either) and document Linux
as build-from-source. A future native decoder via moq-video would remove the
ffmpeg dependency and let Linux ship a binary too.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: kixelated

.github/workflows/libmoq.yml

@@ -119,52 +119,33 @@ jobs:
     needs: release
     runs-on: ${{ matrix.os }}
 
+    # macOS + Windows only. These link the ffmpeg the obs-deps bundle ships
+    # (the same one OBS uses), so the binaries are portable. A Linux build
+    # would link nix/distro ffmpeg and not be portable, so Linux is
+    # build-from-source (see doc/bin/obs.md) and ships no prebuilt binary.
     strategy:
       fail-fast: false
       matrix:
         include:
-          - target: x86_64-unknown-linux-gnu
-            os: ubuntu-latest
-            use_nix: true
-          - target: aarch64-unknown-linux-gnu
-            os: ubuntu-24.04-arm
-            use_nix: true
           - target: aarch64-apple-darwin
             os: macos-latest
-            use_nix: false
           - target: x86_64-pc-windows-msvc
             os: windows-latest
-            use_nix: false
 
     steps:
       - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6
         with:
           fetch-depth: 0
           persist-credentials: false
 
-      - name: Install Nix
-        if: matrix.use_nix
-        uses: DeterminateSystems/nix-installer-action@1d87d45818068401a10cf16bdc5f00b24994a83f # main
-        with:
-          determinate: false
-
       - name: Parse version
         id: parse
         shell: bash
         run: .github/scripts/release.sh parse-version libmoq
 
-      - name: Build and package (Linux, nix)
-        if: matrix.use_nix
-        shell: bash
-        env:
-          TARGET: ${{ matrix.target }}
-          VERSION: ${{ steps.parse.outputs.version }}
-        run: |
-          nix develop --accept-flake-config --command \
-            ./cpp/obs/build.sh --target "$TARGET" --libmoq-release "$VERSION" --output dist
-
-      - name: Build and package (macOS / Windows, native)
-        if: '!matrix.use_nix'
+      # Native Xcode / Visual Studio; libobs/Qt6/ffmpeg come from the obs-deps
+      # bundle and libmoq from the release we just published (--libmoq-release).
+      - name: Build and package
         shell: bash
         env:
           TARGET: ${{ matrix.target }}

doc/bin/obs.md

@@ -59,9 +59,11 @@ just obs build
 
 ## Releases
 
-The plugin statically links `libmoq`, so it ships with every libmoq release rather than on its own schedule. The [`libmoq` workflow](https://github.com/moq-dev/moq/blob/main/.github/workflows/libmoq.yml) (triggered by a `libmoq-v*` tag) rebuilds the plugin against the libmoq release it just published, then cuts a matching `obs-moq-v<version>` release for Linux (x86_64 + arm64, via Nix), macOS (arm64), and Windows (x64). `cpp/obs/build.sh --libmoq-release <version>` drives each per-platform build (it fetches the prebuilt libmoq archive, so no second cargo build).
+The plugin statically links `libmoq`, so it ships with every libmoq release rather than on its own schedule. The [`libmoq` workflow](https://github.com/moq-dev/moq/blob/main/.github/workflows/libmoq.yml) (triggered by a `libmoq-v*` tag) rebuilds the plugin against the libmoq release it just published, then cuts a matching `obs-moq-v<version>` release with **macOS (arm64)** and **Windows (x64)** binaries. `cpp/obs/build.sh --libmoq-release <version>` drives each build (it fetches the prebuilt libmoq archive, so no second cargo build).
 
-The archives are **unsigned**, so macOS Gatekeeper and Windows SmartScreen will warn on first load (right-click → Open on macOS). Extract the archive into your OBS plugins directory: the `.plugin` bundle on macOS, or the `obs-moq/` folder (containing `bin/64bit/` + `data/`) on Linux/Windows.
+The archives are **unsigned**, so macOS Gatekeeper and Windows SmartScreen will warn on first load (right-click → Open on macOS). Extract the archive into your OBS plugins directory: the `.plugin` bundle on macOS, or the `obs-moq/` folder (containing `bin/64bit/` + `data/`) on Windows.
+
+**Linux is build-from-source for now** (see the Linux section above). A prebuilt Linux binary isn't shipped: the plugin needs ffmpeg to decode subscribed video, and a Linux build links the nix/distro ffmpeg rather than the version OBS bundles, so it wouldn't load portably. (A future native decoder via `moq-video` would remove the ffmpeg dependency and let Linux ship a binary too.)
 
 ## Usage