Add installer_util_unittests to the GN windows build

chrome/installer/util/delete_after_reboot_helper_unittest.cc

Index: chrome/installer/util/delete_after_reboot_helper_unittest.cc
diff --git a/chrome/installer/util/delete_after_reboot_helper_unittest.cc b/chrome/installer/util/delete_after_reboot_helper_unittest.cc
index f0acacac059c4d9461bf494cce69643d5dd99d98..8ee4bdcab27e54ecb4583e1c151cf3fc5e1f2cad 100644
--- a/chrome/installer/util/delete_after_reboot_helper_unittest.cc
+++ b/chrome/installer/util/delete_after_reboot_helper_unittest.cc
@@ -53,7 +53,8 @@ class DeleteAfterRebootHelperTest : public testing::Test {
       std::vector<char> buffer;
       StringArrayToMultiSZBytes(original_pending_moves_, &buffer);
       session_manager_key.WriteValue(kPendingFileRenameOps, &buffer[0],
-                                     buffer.size(), REG_MULTI_SZ);
+                                     static_cast<int>(buffer.size()),
+                                     REG_MULTI_SZ);
     }
   }