cares.sh: set CARES_SYMBOL_HIDING=ON

Fixes:
```
00000000000e1e2c T _ares_threadsafety
00000000000cf01c T _ares_timeout
00000000000e1370 T _ares_tolower
00000000000d0854 T _ares_version
! Error: '_a64-mac-sys/usr/lib/libcurl.4.8.0.dylib' exports non-curl symbols.
```
https://github.com/curl/curl-for-win/actions/runs/12969477503/job/36173539375#step:3:6398

cares.sh

@@ -25,6 +25,7 @@ _VER="$1"
 
   # shellcheck disable=SC2086
   cmake -B "${_BLDDIR}" ${_CMAKE_GLOBAL} ${options} \
+    -DCARES_SYMBOL_HIDING=ON \
     -DCARES_STATIC=ON \
     -DCARES_STATIC_PIC=ON \
     -DCARES_SHARED=OFF \