Merge pull request #40433 from apple/compnerd/shared-system

Update build-windows-toolchain.bat

Author: compnerd

utils/build-windows-toolchain.bat

@@ -333,6 +333,7 @@ cmake --build %BuildRoot%\5 --target install || (exit /b)
 cmake ^
   -B %BuildRoot%\6 ^
 
+  -D BUILD_SHARED_LIBS=YES ^
   -D CMAKE_BUILD_TYPE=%CMAKE_BUILD_TYPE% ^
   -D CMAKE_C_COMPILER=%BuildRoot%/1/bin/clang-cl.exe ^
   -D CMAKE_C_FLAGS="/GS- /Oy /Gw /Gy" ^