Release workflow: sh-safe mkdir, arm64 cross libc headers

Both v0.1.0 build jobs failed: packaging used brace expansion under
plain sh (literal '{bin,systemd/user,man}' directory), and the aarch64
job lacked libc6-dev-arm64-cross because --no-install-recommends skips
it, so blake3's NEON unit compiled against host headers.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y42TyF8Zu7NGRR2893vNcZ

.gitea/workflows/release.yml

@@ -36,7 +36,12 @@ jobs:
           apt-get update
           apt-get install -y --no-install-recommends scdoc jq
           if [ "${{ matrix.target }}" = "aarch64-unknown-linux-gnu" ]; then
-            apt-get install -y --no-install-recommends gcc-aarch64-linux-gnu
+            # libc6-dev-arm64-cross is a Recommends of the cross gcc, so
+            # --no-install-recommends skips it — without it cc-rs builds
+            # (blake3's NEON unit) fall back to host headers and die on
+            # bits/wordsize.h.
+            apt-get install -y --no-install-recommends \
+              gcc-aarch64-linux-gnu libc6-dev-arm64-cross
           fi
           rustup target add ${{ matrix.target }}
 
@@ -50,7 +55,9 @@ jobs:
         run: |
           VERSION="${GITHUB_REF_NAME#v}"
           PKG="varde-${VERSION}-${{ matrix.target }}"
-          mkdir -p "$PKG"/{bin,systemd/user,man}
+          # Steps run under plain `sh`, which has no brace expansion —
+          # spell the directories out.
+          mkdir -p "$PKG/bin" "$PKG/systemd/user" "$PKG/man"
           cp "target/${{ matrix.target }}/release/varde-daemon" \
              "target/${{ matrix.target }}/release/varde-ctl" "$PKG/bin/"
           # Cross-strip is unavailable for the foreign target; native