chore: limit to Clang
diff --git a/absl/strings/charconv.cc b/absl/strings/charconv.cc
index db2b392..88bd7ea 100644
--- a/absl/strings/charconv.cc
+++ b/absl/strings/charconv.cc
@@ -347,7 +347,11 @@
     } else {
       ptrdiff_t nan_size = input.subrange_end - input.subrange_begin;
       nan_size = std::min(nan_size, kNanBufferSize - 1);
+#ifdef __GNUC__
+      std::copy_n(input.subrange_begin, nan_size, n_char_sequence);
+#else
       std::copy_n(input.subrange_begin, nan_size, const_cast<char *>(n_char_sequence));
+#endif
       n_char_sequence[nan_size] = '\0';
     }
     char* nan_argument = const_cast<char*>(n_char_sequence);