fix(ci): install Rust target explicitly and disable fail-fast on build

setup-rust-toolchain@v1 was not reliably installing x86_64-apple-darwin
on the arm64 macOS runner, leaving 'cargo build --target' without a
rust-std. Add an explicit 'rustup target add' step and turn off
matrix fail-fast so one target's failure no longer cancels the others.

Author: NAME0x0

.github/workflows/ci.yml

@@ -85,6 +85,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     needs: test
     strategy:
+      fail-fast: false
       matrix:
         include:
           - os: ubuntu-latest
@@ -108,6 +109,9 @@ jobs:
       - uses: actions-rust-lang/setup-rust-toolchain@v1
         with:
           targets: ${{ matrix.target }}
+      - name: Ensure Rust target is installed
+        shell: bash
+        run: rustup target add ${{ matrix.target }}
       - name: Install Linux GUI dependencies
         if: runner.os == 'Linux'
         run: |