Run selective build CI test with more restrictions

Revert reason for #14487 was that internal tests were running with "-Werror,-Wunused-variable" option but not OSS tests

Author: mergennachin

codegen/tools/CMakeLists.txt

@@ -24,7 +24,7 @@ target_include_directories(
 
 # Compile options
 target_compile_options(
-  selective_build PUBLIC -Wno-deprecated-declarations -fPIC -frtti -fexceptions
+  selective_build PUBLIC -Wno-deprecated-declarations -fPIC -frtti -fexceptions -Werror -Wunused-variable
 )
 
 # Link against required libraries

codegen/tools/selective_build.cpp

@@ -186,6 +186,11 @@ get_kernel_tensor_metadatas_from_execution_plan(
 
 const executorch_flatbuffer::Program* _get_program_from_buffer(
     const py::bytes& buffer) {
+  
+  // TEST CODE to trigger CI failure
+  const std::string_view sv = buffer.cast<std::string_view>();
+  void* buf_ptr = const_cast<void*>(static_cast<const void*>(sv.data()));
+  
   return executorch_flatbuffer::GetProgram(
       buffer.cast<std::string_view>().data());
 }