Bucket selection is based on higher 32 bits of seed, which is 64-bit wide only on LP64 platforms.

--- protobuf-3.13.0/src/google/protobuf/map_test.cc.orig	2020-08-15 01:24:06.000000000 +0200
+++ protobuf-3.13.0/src/google/protobuf/map_test.cc	2020-09-10 06:16:47.150949801 +0200
@@ -1005,7 +1005,7 @@
 // small maps. Currently we only have sufficient randomness for debug builds and
 // builds where we can use the RDTSC instruction, so we only test for those
 // builds.
-#if defined(__x86_64__) && defined(__GNUC__) && \
+#if defined(__x86_64__) && defined(__LP64__) && defined(__GNUC__) && \
     !defined(GOOGLE_PROTOBUF_NO_RDTSC)
 TEST_F(MapImplTest, RandomOrdering) {
   for (int i = 0; i < 10; ++i) {