PNaCl driver: Add libgcc to mixed native/bitcode links

tests/toolchain/needs_libgcc.c

Index: tests/toolchain/needs_libgcc.c
diff --git a/tests/toolchain/needs_libgcc.c b/tests/toolchain/needs_libgcc.c
new file mode 100644
index 0000000000000000000000000000000000000000..9d782f4b348bdc89aaf8e4f81e7b13679cc2106d
--- /dev/null
+++ b/tests/toolchain/needs_libgcc.c
@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2014 The Native Client Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include <stdint.h>
+#include <stdlib.h>
+
+int main(int argc, char *argv[]) {
+  if (argc < 3)
+    return 1;
+  uint64_t a = atoll(argv[1]);
+  uint64_t b = atoll(argv[2]);
+  /* 64-bit divide uses a libgcc/compiler-rt call on x86-32 and ARM. */
+  if (a / b == 3ULL)
+    return 0;
+  return 1;
+}