Fix Makefile target 'jtest' on PowerPC (#4357)

Summary:
Before the fix:
On a PowerPC machine, run the following
```
$ make jtest
```
The command will fail due to "undefined symbol: crc32c_ppc". It was caused by
'rocksdbjava' Makefile target not including crc32c_ppc object files when
generating the shared lib. The fix is simple.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4357

Differential Revision: D9779474

Pulled By: riversand963

fbshipit-source-id: 3c5ec9068c2b9c796e6500f71cd900267064fd51

Makefile

@@ -1858,7 +1858,7 @@ $(java_libobjects): jl/%.o: %.cc
 rocksdbjava: $(java_all_libobjects)
 	$(AM_V_GEN)cd java;$(MAKE) javalib;
 	$(AM_V_at)rm -f ./java/target/$(ROCKSDBJNILIB)
-	$(AM_V_at)$(CXX) $(CXXFLAGS) -I./java/. $(JAVA_INCLUDE) -shared -fPIC -o ./java/target/$(ROCKSDBJNILIB) $(JNI_NATIVE_SOURCES) $(java_libobjects) $(JAVA_LDFLAGS) $(COVERAGEFLAGS)
+	$(AM_V_at)$(CXX) $(CXXFLAGS) -I./java/. $(JAVA_INCLUDE) -shared -fPIC -o ./java/target/$(ROCKSDBJNILIB) $(JNI_NATIVE_SOURCES) $(java_all_libobjects) $(JAVA_LDFLAGS) $(COVERAGEFLAGS)
 	$(AM_V_at)cd java;jar -cf target/$(ROCKSDB_JAR) HISTORY*.md
 	$(AM_V_at)cd java/target;jar -uf $(ROCKSDB_JAR) $(ROCKSDBJNILIB)
 	$(AM_V_at)cd java/target/classes;jar -uf ../$(ROCKSDB_JAR) org/rocksdb/*.class org/rocksdb/util/*.class