ci(session-e2e): build Windows arm with zig cgo compiler

windows-latest's default mingw GCC can't compile pkg/apm/webrtc's MSVC SEH
(__try/__except). The repo only builds Windows via zig/clang (.goreleaser.yaml),
so install zig and point CC/CXX at it for the Windows arm.

Author: u9g

.github/workflows/session-e2e.yaml

@@ -58,6 +58,23 @@ jobs:
         if: matrix.os == 'ubuntu-latest'
         run: sudo apt-get update && sudo apt-get install -y libasound2-dev
 
+      # pkg/apm/webrtc's C++ uses MSVC SEH (__try/__except), which the runner's
+      # default mingw GCC can't compile. The repo only ever builds Windows with
+      # zig (clang) -- see .goreleaser.yaml -- so use it as the cgo compiler here
+      # too. Version pinned to match build.yaml's cross-build job.
+      - name: Set up Zig (Windows)
+        if: matrix.os == 'windows-latest'
+        uses: mlugg/setup-zig@d1434d08867e3ee9daa34448df10607b98908d29 # v2
+        with:
+          version: 0.14.1
+
+      - name: Use Zig as cgo compiler (Windows)
+        if: matrix.os == 'windows-latest'
+        shell: bash
+        run: |
+          echo "CC=zig cc -target x86_64-windows-gnu" >> "$GITHUB_ENV"
+          echo "CXX=zig c++ -target x86_64-windows-gnu" >> "$GITHUB_ENV"
+
       - name: Set up Go
         uses: actions/setup-go@4a3601121dd01d1626a1e23e37211e3254c1c06c # v6
         with: