Fix CI: install libc6-dev for the native compiler check

CMake's project(... C) check compiles AND links a test binary, which needs glibc's startup objects (Scrt1.o/crti.o). gcc only Recommends libc6-dev, so --no-install-recommends dropped it and configure failed before the cross-build. Install it explicitly.

.gitea/workflows/release.yml

@@ -22,7 +22,7 @@ jobs:
           apt-get update
           apt-get install -y --no-install-recommends \
             cmake make zip jq curl ca-certificates \
-            gcc gcc-mingw-w64-x86-64
+            gcc libc6-dev gcc-mingw-w64-x86-64
 
       - name: Configure
         run: cmake -S . -B build -DCMAKE_BUILD_TYPE=Release