stage2: put use_llvm and use_stage1 into the Module cache hash

This prevents a compiler_rt built with stage2 (which is intentionally
different than when built with stage1) from being used for stage1 and
vice versa.

Fixes the regression from the previous commit.

src/Compilation.zig

@@ -1177,6 +1177,8 @@ pub fn create(gpa: *Allocator, options: InitOptions) !*Compilation {
             }
             hash.add(valgrind);
             hash.add(single_threaded);
+            hash.add(use_stage1);
+            hash.add(use_llvm);
             hash.add(dll_export_fns);
             hash.add(options.is_test);
             hash.add(options.skip_linker_dependencies);