Fix SDK gem CI: add libclang-dev for Linux, drop Windows from native gem matrix

Author: setoelkahfi

.github/workflows/release-sdk-gem.yml

@@ -41,7 +41,10 @@ jobs:
               runner: macos-15-intel,
               platform: x86_64-darwin,
             }
-          - { name: win-x64, runner: windows-2022, platform: x64-mingw-ucrt }
+          # Windows is excluded: rb-sys bindgen fails because RubyInstaller is
+          # MinGW-based and its rbconfig emits GCC flags that are incompatible
+          # with the MSVC clang used by bindgen. The source gem provides a
+          # fallback for Windows users (compiled at install time).
 
     steps:
       - name: Checkout
@@ -80,6 +83,10 @@ jobs:
             done
           done
 
+      - name: Install system dependencies (Linux)
+        if: runner.os == 'Linux'
+        run: sudo apt-get update -q && sudo apt-get install -y libclang-dev
+
       - name: Read Rust toolchain
         shell: bash
         run: |