feat(package-npm): use aarch64 gcc for arm64

Installing the toolchain is not enough. `CC` & `CXX` must be explicitly
defined. If we set `STRIP` for the `--strip` option then `prebuildify`
won't copy the binary to the `prebuilds` directory for whatever reason.

Fixes #22

.github/workflows/package-npm.yml

@@ -104,13 +104,16 @@ jobs:
             cd - > /dev/null
           done < <(find . -name grammar.js -not -path './node_modules/*' -not -path './.build/*')
       - name: Build x64 binary
-        run: npm x -- prebuildify --arch x64 -t 20.9.0 --strip
-      - name: Build arm64 binary
-        if: runner.os != 'Linux'
-        run: npm x -- prebuildify --arch arm64 -t 20.9.0 --strip
-      - name: Build arm64 binary
+        run: npm x -- prebuildify --arch x64 -t 20.9.0
+      - name: Set up cross-compilation
         if: runner.os == 'Linux'
-        run: npm x -- prebuildify-cross -i linux-arm64 -t 20.9.0 --strip
+        run: |-
+          sudo apt-get update
+          sudo apt-get install g++-aarch64-linux-gnu
+          printf '%s\n' >> "$GITHUB_ENV" \
+            'CC=aarch64-linux-gnu-gcc' 'CXX=aarch64-linux-gnu-g++'
+      - name: Build arm64 binary
+        run: npm x -- prebuildify --arch arm64 -t 20.9.0
       - name: Upload binaries
         uses: actions/upload-artifact@v4
         with: