https://github.com/protocolbuffers/protobuf/issues/11996

Fix run-time error on aarch64:

```
$ protoc
CANNOT LINK EXECUTABLE "protoc": cannot locate symbol "_ZN6google8protobuf8internal20VarintParseSlowArm32EPKcPjm" referenced by "/data/data/com.termux/files/usr/lib/libprotoc.so"...
Aborted
```

--- a/src/google/protobuf/parse_context.cc
+++ b/src/google/protobuf/parse_context.cc
@@ -730,6 +730,7 @@
 constexpr uint64_t kFirstResultBitChunk8 = 8 * 7;
 constexpr uint64_t kValidBitsForInvalidVarint = 0x60;
 
+PROTOBUF_EXPORT
 PROTOBUF_NOINLINE const char* VarintParseSlowArm64(const char* p, uint64_t* out,
                                                    uint64_t first8) {
   SlowPathEncodedInfo info = ComputeLengthAndUpdateP(p);
@@ -768,6 +769,7 @@
 
 // See comments in VarintParseSlowArm64 for a description of the algorithm.
 // Differences in the 32 bit version are noted below.
+PROTOBUF_EXPORT
 PROTOBUF_NOINLINE const char* VarintParseSlowArm32(const char* p, uint32_t* out,
                                                    uint64_t first8) {
   // This also skips the slop bytes.