[RocksJava] JavaDoc is executed too often

Previous to this commit too much targets got dependencies
on javadocs target.

Introduced one additional target "javalib" which resolves
that situation. JavaDoc will now be generated once while
executing a task with prefix "rocksdbjava".

Makefile

@@ -594,7 +594,7 @@ libsnappy.a:
 
 rocksdbjavastatic: libz.a libbz2.a libsnappy.a
 	OPT="-fPIC -DNDEBUG -O2" $(MAKE) $(LIBRARY) -j
-	cd java;$(MAKE) java;
+	cd java;$(MAKE) javalib;
 	rm -f ./java/$(ROCKSDBJNILIB)
 	$(CXX) $(CXXFLAGS) -I./java/. $(JAVA_INCLUDE) -shared -fPIC -o ./java/$(ROCKSDBJNILIB) $(JNI_NATIVE_SOURCES) $(LIBOBJECTS) $(COVERAGEFLAGS) libz.a libbz2.a libsnappy.a
 	cd java;jar -cf $(ROCKSDB_JAR) org/rocksdb/*.class org/rocksdb/util/*.class HISTORY*.md $(ROCKSDBJNILIB)
@@ -615,7 +615,7 @@ rocksdbjavastaticpublish: rocksdbjavastaticrelease
 
 rocksdbjava:
 	OPT="-fPIC -DNDEBUG -O2" $(MAKE) $(LIBRARY) -j32
-	cd java;$(MAKE) java;
+	cd java;$(MAKE) javalib;
 	rm -f ./java/$(ROCKSDBJNILIB)
 	$(CXX) $(CXXFLAGS) -I./java/. $(JAVA_INCLUDE) -shared -fPIC -o ./java/$(ROCKSDBJNILIB) $(JNI_NATIVE_SOURCES) $(LIBOBJECTS) $(JAVA_LDFLAGS) $(COVERAGEFLAGS)
 	cd java;jar -cf $(ROCKSDB_JAR) org/rocksdb/*.class org/rocksdb/util/*.class HISTORY*.md $(ROCKSDBJNILIB)

java/Makefile

@@ -97,7 +97,9 @@ clean:
 javadocs:
 	mkdir -p javadoc; javadoc -d javadoc -sourcepath . -subpackages org -exclude org.rocksdb.test
 
-java: javadocs resolve_test_deps
+javalib: java javadocs
+
+java: resolve_test_deps
 	javac org/rocksdb/util/*.java org/rocksdb/*.java
 	javac -cp $(JAVA_TESTCLASSPATH) org/rocksdb/test/*.java
 	@cp ../HISTORY.md ./HISTORY-CPP.md