chore(deps): update rust crate syn to v3.0.7

.gitea/workflows/build.yml

@@ -60,11 +60,9 @@ jobs:
         with:
           toolchain: ${{ startsWith(matrix.target, 'mips') && 'nightly' || 'stable' }}
           cache: false
+          build-warnings: warn
 
       - name: Install cross and binary tools
-        env:
-          # Upstream cross warnings must not block installing the build tool.
-          CARGO_BUILD_WARNINGS: warn
         run: |
           sudo apt-get update
           sudo apt-get install -y --no-install-recommends binutils llvm
@@ -73,7 +71,8 @@ jobs:
 
       - name: Build release binary
         env:
-          RUSTFLAGS: -C target-feature=+crt-static
+          # MIPS build-std lacks Rust's bundled CRT objects; use the cross GCC copies.
+          RUSTFLAGS: ${{ startsWith(matrix.target, 'mips') && '-C target-feature=+crt-static -C link-self-contained=no' || '-C target-feature=+crt-static' }}
           # Copy toolchains and sources instead of translating nested bind mounts.
           CROSS_REMOTE: "true"
           # Cross's per-artifact JSON capture hides compiler diagnostics.

Cross.toml

@@ -7,6 +7,15 @@ image.toolchain = ["linux/arm64=aarch64-unknown-linux-gnu"]
 pre-build = [
     "apt-get update && apt-get install -y --no-install-recommends pkg-config",
     'echo "set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY BOTH)" >> /opt/toolchain.cmake',
+    # Rust's musl std links -lunwind; MIPS cross GCC supplies the unwinder as libgcc_eh.a.
+    '''
+    for cc in /usr/local/bin/mips*-gcc; do
+        [ -x "$cc" ] || continue
+        archive=$("$cc" -print-file-name=libgcc_eh.a)
+        test -f "$archive" || exit 1
+        ln -sf libgcc_eh.a "$(dirname "$archive")/libunwind.a"
+    done
+    ''',
 ]
 
 # This target's image was added after the cross 0.2.5 release.